I come in on AA from MIA at this time and though I use NEXUS the customs arrival hall is so empty you can hear crickets chirping. I am surprised there is another flight on AA arriving at this time because I didn't see a soul. When you go out after customs exit the terminal is practically empty.

I don't know how long your bags will take but not that long. I checked bags once a few months ago and the bag came in about 10 minutes after I arrived at the carousel.

Then go up the first escalator you find as you are basically underneath the International departures area and CX is the only flight leaving that late.

F check-in for CX is fast as there are at most only 6 people using it and security is located right next to check-in and at that point is is just for that flight. I usually go around 11 p.m. and it is empty, but you will be behind a raft of (300 +/-) Y passengers who have been there since 11 p.m. or earlier so you might have a bit of a queue.

I don't think CX would leave an F passenger behind who has checked in and they have to be aware of the security volumes. On the plus side from 11-1215 they will have probably processed 3/4 of the passengers. When I arrive at 11 the Y check-in line is packed.

All that said I think 90 minutes is cutting it too close for AA arriving (or leaving ORD) on time to be frank. Not for YYZ but for AA you are giving them a lot of credit. I just changed a YYZ MIA reservation for Friday from the 830 flight to the 610 flight as they have been late every day for the last 3 days on the 830 and I would miss my connection.

Why would you post this in the AC forum for a AA/CX flight pair? This should be moved to the AA forum and there are lots of people there who know YYZ.