The question before the high court revolved around whether former Vivendi employee Michel Dell'Aniello could represent all retirees who were eligible for health benefits under the company plan.
Before it was bought by Vivendi, Seagram Co. set up a health plan that covered employees while they worked for the company and after they retired.
Seagram changed its plan in the mid-1980s and added a footnote that had not been in the original 1977 plan indicating that the company reserved the right to change or suspend the plan or increase the amount paid by employees and retirees.
In September 2008, new owner Vivendi announced it would raise the plan's annual deductible, only cover certain prescription drugs and set a lifetime total of $15,000 for all coverage under the plan.
Dell'Aniello filed a motion to launch a class action against Vivendi, but Quebec's Superior Court didn't allow it.
However, the Quebec Court of Appeal overturned the lower court ruling and the matter made its way to the Supreme Court, which released a 7-0 decision Thursday in favour of Dell'Aniello.
In order for a class action to proceed, there must be a common question of law or fact that affects all members of the proposed suit.
In the case of Dell'Aniello's class action, the Supreme Court says the main question that binds all the members together is whether the changes to the benefits plan were lawful.
The court said that overarching question applied to all members of the benefits plan, even if their individual circumstances differed and so a class action could proceed.
"In short, it can be concluded that the common questions do not have to lead to common answers," read the decision.
"At the authorization stage, the approach taken to the commonality requirement in Quebec civil procedure is a flexible one.
"As a result, the criterion ... may be met even if the common questions raised by the class action require nuanced answers for the various members of the group."