I've found the YCG agents to be very flexible (much more flexible than the call-centre). I would suspect that if your flight is canceled, and they would work with you to get you to NY.

Flights can be canceled for days in a row, so if your scheduled flight gets canceled, I'd just hop a bus to Vancouver or Calgary (but make sure the YCG agents know what you are doing, so your subsequent flight leg(s) don't get canceled). The bus is painful, but it will get you there.