It is due to section 30 of Canada’s Broadcasting Distribution Regulations’ simultaneous substitution provisions. As long as a Canadian broadcaster is broadcasting the same show at the same time, cable companies and others distributing the Canadian signal have to substitute the Canadian signal for the American signal, when requested by the Canadian broadcaster. Thus, you are not really watching the American station. It is one of the stupider attempts to favour Canadian cultural industries. They tell the public that such policies are supposed encourage the Canadian identity. However, in this case, the policy actually gives broadcasters an incentive to air American rather than Canadian content. If they air American content, as long as it is at the same time as an American station, their signal is substituted for the American station’s signal and they can charge advertisers for both audiences. However, it they air a Canadian program, if is unlikely to also be carried by the American station, so they can only charge advertisers for their own signal
This is one reason TV guides are often wrong when it comes to Canadian broadcast times. The Canadian broadcasters tend to wait until the Americans have announced their schedule so they can broadcast shows at the same time.
