This is not as simple as you think. Just because a politician makes a law, does not mean that the law is valid. As such there have already been challenges, and you may remember that the previous set of laws were tossed due to similar grounds. Recently an escort agency in Toronto disputed the legality of the c36 laws, and won, as the judge agreed.
I'm not a lawyer, and this is not legal advice, however, most cities issue licenses for escort agencies, and Vancouver does have an authorized brothel area. Some interesting reading below.
https://www.justice.gc.ca/eng/rp-pr/csj-sjc/jsp-sjp/rr02_9/a.html
https://globalnews.ca/news/6580684/ontario-judge-rules-bill-c-36-unconstitutional/
In regards to how agencies work, or at least how they should work. Despite appearances, an agency is not an employer, but rather is often hired by the girls for phone booking, screening, safe incalls, advertising, safety checks, and of course their contact list. Especially when a girl is travelling from one area to another (girls don't usually like to work where they live for privacy reasons), she may find that an agency is simply safer than going it alone and having no idea who is good or bad. Not only that, if you are working, you can't answer the phone, and having to answer messages all night even when you are "off" can get pretty annoying. One girl can easily receive 100-200 messages in a day, including constant dick pics and haggling etc. ,At the end of the day each girl decides what's best for her. Of course I am sure there are all sorts of different arrangements out there.
I think it's pretty clear that girls have the right to hire whoever they want to increase their safety as well as add some convenience. It's in my experience the girls who hire the agency, not the other way around, and as such it's typically the girls who handle the financial transactions with clients rather than the agency. Of course as I said, I can only speak from my own experience, and who knows what other arrangements are out there, but that's how we see it.