Geoff, AC had several flights a day into Varadero, which is only a 2 hour bus trip from Havana itself, during last year's northern winter as well as flights into HAV from Montreal as well as the daily from YVR.
Flights into Vardero last northern winter season offered by AC were from YVR YYC YYZ YUL YHZ & YOW from memory. They may not be showing as yet, but I'd check aeroplan.com to see if anything from YYC to VRA in particular is loaded and available for reward bookings.

Other Cuban destination options, (although slightly further away from HAV than what VRA is), that AC offer would be Cayo Coco, Holguin and another Cayo something or other! AC offers 5 destinations in Cuba over the winter season.
Cheers.