THERE'S a pause on the line from Toronto.

"Was it really 25 years ago?", laughs Margo Timmins. "Oh my God. I had no idea." I check the liner notes on the Cowboy Junkies' career-making album, The Trinity Session, and sure enough, there it is: November 27, 1987. A quarter of a century has passed since Margo and her colleagues slipped into Toronto's Church of the Holy Trinity, a place of God in the heart of the city.

Using a single Calrec Ambisonic microphone – the method they had pioneered on their debut, Whites Off Earth Now!, two years earlier – the Junkies recorded, live, a dozen songs, half of them originals. The church, incidentally, had been opened in 1847 thanks to a gift from a woman from Settle in England.

The Junkies – Margo (voice), brothers Michael (guitar) and Peter (drums), and Alan Anton on bass – seemed to know they were on to a good thing. The Trinity Session – with its dream-state version of Lou Reed's Sweet Jane, an exquisite reading of Hank Williams's I'm So Lonesome I Could Cry, and Margo and Michael's instant classic, To Love Is To Bury – attracted rave reviews, established the band's name and created a whirlwind of attention.

Rolling Stone, no less, declared: "[It] is in the great tradition of albums that establish a mood and sustain it so consistently that the entire record seems like one continuously unfolding song. The mood in this instance is hypnotic and introspective – an intense, melancholic longing that blends the elemental emotions of country music and the blues with the poetic world-weariness of the Velvet Underground."

Margo well remembers her mother's reaction to the new music. "The morning after the Trinity session, Mike came by the house with the tape, because that's all there was – there was no overdubbing or anything – and said, 'You've got to hear this'. My mum lived in the suburbs but she'd driven downtown because she was taking my other brother, John, to the train station – he'd come in to play on the session. She popped in for breakfast and happened to be there when Mike came by, which is odd, because my mum never just popped in. You don't just pop into your [twentysomething child's] house, you never know what you're going to see! But she did that morning, and we played the tape, and my mum – who enjoys music, but knows nothing about it – listened to it and said: 'Your life will never be the same'. I thought that was cryptic. But she was right, you know. It never has been the same since."

The album established a certain template for the Junkies' sound in the public imagination – hushed, somnambulant alt-country – but this has long been deceptive, through albums such as Pale Sun Crescent Moon (1993), Open (2001) and At The End Of Paths Taken (2007). The terrific recent four-album Nomad series, released over 18 months – Renmin Park, Demons, Sing In My Meadow and The Wilderness – shows off a gutsier, more eclectic approach altogether.

Demons, the second volume, released last year, was a moving collection of covers of songs penned by the late Vic Chesnutt who, along with Ryan Adams and Natalie Merchant, had been a special guest in November 2006 when the Junkies revisited Trinity, documentary crew in tow, to celebrate the 20th anniversary of that album. Chesnutt died on Christmas Day, 2009.

"[Vic] was a very unique person ... It was a very scary project because Vic's fans are seriously loyal and you don't tamper with a Vic Chesnutt song, especially just after his death," Margo reflects. "We were fans too, so we really did understand what we were doing. Vic's songs are very complicated and lyrically complex. It was a difficult album to do emotionally and on a skill level. My problem is I don't ever want to offend anybody. I really don't have the rock'n'roll attitude." She laughs: "I'm a good Catholic girl – there's lot of guilt here! I really was nervous that we would offend people who were seriously mourning [Vic], but we didn't. We got tons of letters afterwards from Vic's fans who hadn't played his music since he died, and this was a way back into it. That was just so rewarding."

If one thing is evident from even a cursory glance at the band's history, it is that they have always taken risks, done things their own way. "I don't think the band ever paid too much attention to what was or wasn't in style," says Margo. "When we were with record labels they were always trying to get us to write the big hit, and of course we would have loved to have written the big hit, but our main goal was longevity. We wanted to continue to love what we were doing and we knew that if we went down tracks that were uncomfortable to us, maybe it would have been financially successful, but it might have destroyed us as a band.

"We've always been really protective of us as a band; we are really insular. I think that is a part of why we are still together and enjoy each other's company and why we still enjoy playing music." She laughs again. "It's probably also the reason I still have to work so hard, but that's okay ..."

The band tour frequently – they supported John Mellencamp across Canada this summer, are doing a few European dates this month, and are back on the road in January, starting with a Celtic Connections show at Kelvingrove Art Gallery and Museum, a perfect venue for the Junkies. They do seem to be a hard-working group.

"Nowadays you have to be," concedes Margot. "We always have been, but nowadays it's more of a necessity than anything else. In the old days you used to make your money by several different ways; now, really the bulk [of income] comes from touring. If you want to pay your mortgage, that's what you've got to do."

They also make diligent use of the internet, with a full website (at latentrecordings.com/cowboyjunkies) and a regularly updated blog. "The website's been the greatest tool we've had since going independent," Margo says. "Even in the early days, I always made myself accessible to everybody; I've always invited everybody to stick around after the show. The whole website is just an extension of that."

She agrees that one of the Junkies' unsung strengths has been the consistent quality of her brother Mike's songwriting. While acknowledging the attention that has been paid over the years to her voice and the band's distinctive sound, "the lyric side has been kind of hidden, overlooked, but I think people will one day say, 'You know, that guy could write'".

In their downtime between touring and recording (the band has just opened a new Toronto studio, The Hangar), the four Junkies, all of whom are within sight of (if not actually over) 50, have blissfully ordinary lives. Margo talks about them "all having kids and spending time at hockey games, soccer, school yards, the principal's office and all that sort of stuff." But the road beckons yet again. Mention of Mellencamp reminds her that the band once opened for people as diverse as Sting and Bruce Hornsby.

"When the Mellencamp thing came up, we thought, let's give it a go – we haven't done it in a long time. We didn't like it in the early days, but I think we weren't ready as a band. To be an opening act you have to really come on with attitude, because no-one's listening, everybody is coming in or going out, they're reading their magazines or texting. If you're an insecure band, that can be overwhelming. But now that we're old and crochety, it was sort of fun."

She laughs again. "It was quite fun touring with Mellencamp, but we're not going to make a career [of opening for others]. The tours that are planned in the next eight months are mainly just us. That works for our audience, I think." Twenty-five years after the Trinity Session established their reputation, it works for the Cowboy Junkies, too.

Cowboy Junkies play Kelvingrove Art Gallery and Museum, Glasgow, on January 23 as part of Celtic Connections; for details, see www.celticconnections.com. The Celtic Connections programme will be free with next week's edition of the Sunday Herald.

www.celticconnections.com