I'm not sure I can answer that, but the Statistics Canada website would be the source to consult. They have a clear explanation of how they set up their CMAs. My understanding is that they start with a city with a certain minimum core population and then look at cities around that. If there are enough people commuting to work in the core, for instance, and vice versa, they will include that. They'll do their work like that, and increase the region, as long as any nearby city meets these criteria. They will look at the map, and if there are holes in that map, they will fill these holes, and that will be the CMA. That's how they create that.
On November 6th, 2018. See this statement in context.