AC only flies to Toronto, Montreal and Vancouver from Mexico City
There is no nonstop weekday flight between Mexico City and Denver, btw. This has been a very rough stretch. It is theoretically possible that some guys are coming back to Toronto on that flight, and going back to Denver tomorrow. It's not like anyone is seriously practicing today or tomorrow, and while it's three hours extra flying, vs changing in Dallas or something, you get to sleep in your own bed for a night.
I know lots of people that might do that in the middle of a gruelling 10 day business trip.