Technically speaking this is new for Air Canada although if you flown recently many passengers were already doing this without permission but Air Canada will now allow passengers to use their cell phones after the aircraft they are on has left the active runway:
From Air Canada:
Effective October 18, 2010, customers on board all Air Canada and Jazz operated flights will be permitted to use their handheld electronic devices, such as cellular phones, Blackberries and smart phones during the taxi-in to the gate after the aircraft has turned off the active runway.
The handheld electronic devices must be retrieved prior to landing as all carry on bags must be stowed until the seat belt sign is turned off at the gate. Flight attendants will advise customers when mobile phones can be used after arrival.