1. MBA ranking is just 1 critiria when you choose which MBA program is right for you. You should also look at some thing else, like the reputation of the University, the focus of each program, etc.
2. You should look for as many rankings as possible to get a whole picture of it. For example, Financial Times rankning, since it is a MBA ranking conducted by Financial Times magazine of UK, it is not well known in the US. But it is still a good reference, because it is a world wide MBA ranking. The rankings I found available for Canadian MBA programs are Financial Times, Canadian Business and Business Week.
3. Look at the detail ( every catagary ) in the rankings and find out which are important for you. For instance, I think the % of female students and faculty in Canadian Business ranking is not so important to me. If you get rid of this 2 catagary by yourself, the ranking will be a whole new story.
Good luck in your MBA searching.