In Quebec, if I'm not mistaken, with the exception of McGill University and HEC Montréal, all universities have collective agreements, that is to say professors have a union. We haven't looked at it in detail, but where there is a collective agreement and a union, the gender gap is much smaller than in universities where there isn't that kind of support, which contributes enormously to reducing those gaps.
It's also very rare for men to negotiate market premiums when they are recruited. When there is a collective agreement that allows this or that causes these market premiums to disappear over the years, they serve as a power of attraction for some professors. At Polytechnique, they wanted to get rid of all the premiums that existed and adopt a much more egalitarian approach. If you look at the rest of Canada, I think you have part of the answer in terms of who is unionized and who is not.