Unions such as Unifor and Canada’s Building Trades Unions have programs that run the gamut, because it is a complex problem. There are pre-apprenticeship programs that try to attract women or under-represented workers to have them get some of the skills necessary to enter the trades. They mentor people at work and they try to provide a work environment.
I was in the naval reserve, so I've worked in very male-dominated environments. Sometimes cultures arise that are hostile to people from outside of that culture. They work with mentors to change the culture to make it more welcoming to people who are coming through. It's not, obviously, just getting them into training; it's getting people to complete the training and into jobs.