Senior Labour sources say Miliband's move to one-member-one-vote (OMOV) does not apply to the election of the Scottish leader, and will have to be implemented separately by Lamont.
The biggest changes to Labour since Tony Blair rewrote Clause IV on the aims and values of the party were last week backed by Miliband.
His review, conducted by Labour peer Lord Collins, was triggered by trade union Unite's actions in a selection contest in Falkirk, exposed by the Sunday Herald.
Miliband is backing changes to make trades unionists "opt in" to paying part of their political levy to Labour. More controversially, he backs abolition of the decades-old electoral college that helped secure him victory in 2010 against his brother, David.
The college has three sections, with MPs, constituency party members and members of organisations affiliated to the party, such as trades unions, all getting the same weight of vote in any contest.
Collins is believed to have recommended a move to OMOV, to give everyone balloted an equal say.
But the changes will not automatically apply to the election of the Scottish Labour leader, as procedures are devolved.
Insiders say Lamont is highly likely to implement the same reform, as it would look bad to retain an archaic system.
One source said: "Miliband is implementing these changes because of a problem that emanated from Scotland. Johann will have no choice but to change the outdated system here as well."
With trades unions at UK level backing changes to the college, unions are unlikely to object to similar reforms in Scotland.
But the timing of change could prove tricky for Lamont. Miliband's reforms are expected to be ratified at a special conference on March 1.
The Scottish Labour conference is three weeks later, which could make the timescale tight, one insider said.
Scottish Labour could make the change at a special conference after the independence referendum.
The college system delivered victory for Lamont in the 2011 leadership contest. Ken Macintosh won the ordinary members' vote, but Lamont triumphed with ther backing of MSPs, MPs and unions.
At a UK level the biggest resistance to changing the system is believed to be from MPs unhappy that their one-third vote share will end.
But the new rules are likely to give MPs a huge say in who could stand in future leadership contests, with potential candidates needing backing from up to 25% of Labour MPs to get on the ballot paper.
A Scottish Labour spokesperson said they looked forward to seeing details of the review and would make any necessary changes.