Since I normally fly out of YYZ in BR and it is probably the last flight out, they may have it easier than AC but their boarding process everywhere I have flown with them is the same. They have more staff and each one stands with a board that has your Zone on it. Then they come and check your boarding card to see what zone number. If you are in the wrong queue they send you to the correct queue. With AC it is a free for all. One stands up and everyone stands up.
Sometimes I wonder if all the passengers on the flight are either Zone 1 or Zone 2 because everyone seems to be in the same queue.