No new major cost overruns, delays or major rows have emerged. In fact, there’s been some good news to report. Princes Street was opened up to traffic again at the end of November following a frantic burst of construction activity to complete track laying on the iconic thoroughfare.

The street became an emblem of everything that was going wrong with the project earlier in the year when a dispute with German construction firm Bilfinger Berger led the firm to down tools for a month so it must have been heartening for tram leaders to see this section of work complete.

Transport Initiatives Edinburgh, the council-owned company overseeing the project, also managed to win the first of a number of formal contractual disputes with the consortium building it, made up of Bilfinger, Siemens and CAF (BSC), after they were referred to an independent arbitrator.

And, as The Herald has reported, work is continuing apace on a number of major civil engineering projects to construct the viaducts and walls that will support the tram system.

But it’s hard to feel celebratory about this troubled, £545m project, despite its promise to transform Edinburgh’s public transport infrastructure. It’s a bit like being at a wedding where you know the groom is having an affair - plenty of reasons to seem cheerful but they don’t quite make up for the nagging doubts that are lingering.

Scratch beneath the surface and it’s clear that the major problems affecting the project have not gone away.

In an interview with The Herald earlier this week, Susan Clark, deputy project director at Tie, conceded that present work levels are lower than they would have been if it were not for the continuing stand-off with BSC.

In other words, delays to completing the tram system - which has already been put back at least seven months to February 2012 - are likely to mount up, given the current workrate. Tie later declined to say exactly - or even roughly - what the current work levels were as compared to target levels, making it difficult to say how much the overall completion date is being pushed back.

The areas affected by the dispute include track laying from Newhaven to the foot of Leith Walk, Leith Walk itself, Picardy Place, York Place, Shandwick Place and Haymarket, all of which have been on hold for around five months. This “on street” section work represents 42% over the overall project and only 7.7% of that is complete. So that’s just over a third of the project where work is currently at a standstill.

At the heart of the dispute is a disagreement between Tie and BSC over how to handle changes to the original design specification. Some of these are routine and others thrown up by unexpected ground conditions - with a whole manner of underground chambers, graves and other surprising configurations thrown up by work to divert water, electricity and gas mains. BSC want Tie to shoulder the risk - and cost - of any changes while Tie claims it has put contractual arrangements in place that are flexible enough to handle them.

Separate to that disagreement is a contractual wrangle over the added cost of design changes made so far. At the last count, six matters had been put into a formal dispute procedure, out of more than 400 points of contention. Tie’s initial victory, sources suggest, was on a relatively minor point with little cost associated. Estimates vary wildly but the potential cost of meeting all of BSC’s claims has been put at up £100m.

When Tie announced in August that it was “very unlikely” to stay within its £545m budget, it also undertook to provide the City of Edinburgh Council with an update in January on a revised cost and timeframe. It has since been unable to spell out exactly what the cost of the project will be or when it be completed.

Amid the fog, two versions of events have emerged. One, explained to me in September by Tie’s chief executive, Richard Jeffrey, was that there was uncertainty over a relatively small part of the tram project and a high degree of certainty over the remainder. His hope is that the issues currently proceeding through the formal dispute resolution procedure will lay the ground for a new, robust basis to proceed and the costs will be contained through a vigorous defence of BSC’s claims.

Critics, including John Carson, the former head of maintenance at Network Rail, have put forward an opposing theory: that uncertainty has become endemic to the project and that we are unlikely to see any closure on the disputes that have damaged it so far by January.

“The real issue here is that at the current rate of spend, Tie will irrevocably be committing City of Edinburgh Council to these costs. If they were to foreshorten the project either terminating it at Haymarket or Princes Street then they should by now have made the decision and focus their efforts in those areas to the exclusion of all else,” he said.

According to Ms Clark, a lot of work has gone into preparing and planning for the next stage of on-street work, including issues such as road diversions. A revised programme of works, with amended timescales, will be presented in January to the council and other stakeholders. “A lot of work has done between us and the contractor in the last few weeks. Part of the overall discussion is the programme and things we might want to do to improve the programme. When those discussions are completed we will put forward a revised date for the programme,” she said.

And does that mean that Tie will be able to put a firm figure on the costs or give a robust completion date? Susan Clark’s answer is a little less than categorical: “I’m confident that a lot of work is going into that at the moment. It’s a very complex process that we’re working through. We have told people that we’ll be in a better position in January, that’s what we’re working towards.”