I don’t think anyone suggested anything about unions withholding labour.
Unions will be sitting on the other side of any EBA variations Bain may desire.
They do not have to agree, and as always, the employees will have the final say. They may be guided by the unions in their vote.
So yes, the unions do have a lot of say in Bain’s future cost of doing business.
There may always be a threat of outsourcing, but that will be up to the unions (and the employees) to weigh up during negotiations.