The problem with Canada Place is once you get down into the bowels of the building to start the process, where are they going to make you wait? Or will they send early passengers back out to the street or up into the hotel? I hope they'll at least accept the luggage.
When I boarded Queen Victoria in Southampton last fall, they were holding early arrivals in a queue alongside the terminal building. Priority passengers (Grills, Diamond, Platinum) got waved through, so I went right in and checked in quickly. The odd thing is that there weren't many people in the building and most of the check-in staff had nobody in front of them. It seemed like a waste of person-hours to have staff doing nothing while there were people who could be checked in. There was plenty of seating, too. But that's their rule and they stick to it.