I have been using the Sunpass East for close to a year now and the routing coming up for YOW-LAS is a bit limited. I think it limits the number of option to about 5.

Sometimes I have trouble getting the LAS-YYZ-YOW on the red eye to come up. I have had success in forcing the connection I want to come up by putting the departure time. I think AC don't put the YOW-YUL Jazz flight on option since it is a small plane with only 43-47 seats and can sometimes be full. It is rare for YOW-YYZ to be full.

I have had success changing my flight to get a longer layover in YYZ in order to process a TN visa since those options do not come up on the pass. Not sure if AC would allow you to do a different routing though.