Can't speak to other Canadian airports but baggage at YYZ can be a PITA. Doesn't matter what airline. Even with UA over the years and the different people they've had outsourcing it (at different points at least three I can think of: AC, Swissport and the current company).

Sometimes bags are rolling off shortly after being in the baggage area, other times it can be 30 minutes. IMO, I think it's a GTAA problem. For clarity, I have NEXUS so am usually in the hall pretty quickly.

Priority is definitely YMMV, but that's common in the US anyway - priority bags just often aren't on the belt first. Timing of the first bag can vary, again, regardless of carrier. For example, coming off the AC ZRH flight in May, I waited 60 minutes for my bag (priority) - I think it took about 45 minutes for the first to come out from the flight, so obviously priority wasn't being accounted for. However, coming in from CVG a couple of weeks ago, also AC, my bag was off pretty close to first, so priority did work, and bags were rolling within about 5 minutes of getting to the claim area. So again, YMMV.