I think AA is a bit sneaky here. Under Canada passenger rights, they are to rebook on other airline for delays in excess of 3 hours even if outside of airline control. AA is keeping the delay as 2h when it is not realistic for PIT-LGA to make it into LGA. Meanwhile AC flight is delayed by mere 45 min which AA is unwilling to rebook.... until it was too late to be booked on the AC flight.