Now, if Mulcair could produce some (current) Quebec labour endorsements, that would be something.What might be even more interesting would be the Quebec labour endorsements going to other candidates.
Don't hold your breath. Unions in Québec fall into a few (fluid) categories: 1. Those who support the BQ and PQ. 2. Those who support individual candidates based on their record and stand. 3. Those who traditionally do not support any party. #1 and #2 tend to change back and forth with time and based on elections.
Some individual leaders may publicly support QS provincially.
If there is a union in Québec, or a principal leader of a union, who has expressed support for the NDP (never mind for a leadership candidate), that would be news to me - with the sole exception of those individuals in various unions (none of them leadership types) who have been elected in the Orange Wave.