In the case of scholarships, it is indeed the research councils that set the amounts. However, post-doctoral fellows are often Mitacs fellowships at the Canadian level. The typical income for Mitacs fellows is $40,000 plus $5,000 for equipment. Some awards are higher.
For example, one of my colleagues at one point received a $53,000 award. However, when he was awarded it, what he wasn't told was that employer expenses would be deducted from it, and they are typically 13% to 20% of the total, depending on the job. So my colleague was paid less than $45,000 per year, when he was promised $53,000 gross income.
This is another problem and is something that isn't announced to the post-doc before they take the job. That should be clear. If not, the award should be announced, but then supplements for employer charges should be added so that the university can pay the post-doc the amount announced, without breaking its word.