I'm sure the government took advice from its lawyers regarding the Constitution, but I don't imagine there was a lot of time spent on that. Clearly, they are responsible for immigration, and they recognized there was a need for a program to facilitate the assimilation of immigrants into Canada professionally, so they launched this program to try to make the provinces into some kind of level playing field.
They haven't legislated, I don't believe, for this program. I stand to be corrected, but I don't believe they have legislated for this program. Were they to legislate for this program, they would have the burden of showing that the legislation, if it touched labour or education, was necessarily incidental to their immigration jurisdiction. It might be hard to show that regulating professional qualifications was necessarily incidental to immigration. That might be a bit of a stretch. “Necessarily incidental” means you can't really do a job in this field unless you also deal with these issues. You can't really regulate airlines unless you deal with their labour problems. That's why you have a Canada Labour Code. You can't really legislate on banking unless you have the power to deal with some other issues that arise under banking.
Can you not deal with immigration without dealing with professional qualifications? That's the question? Arguably you might well be able to adequately deal with immigration issues without dealing with labour or education. But that's the issue. Anything they did in the area of education or labour would have to be shown to be necessarily incidental to their exercising their legislative authority over immigration.