Requirement of GRE score vary from department to department. As for example, in UBC, application forwarded to the Economics department must be accomplied with a GRE score, whereas for Biomedical engineering, GRE score is not required. So only through browsing the specific school website you can get the exact information. But in general, as per my knowledge, all the well ranked universities in Canada ask for GRE score. Even if you apply to a school where GRE score is not a mandatory, a candidate who applies with a GRE score will be definitely given priority.
Almost all the universities ranked in the top 100 (even outside USA and Canada) asks for GRE score.
So, to be on the safeside, get your score first and then apply to your desired school. It will fortify your chance for sure.