This isn't fully true. At least in Alberta, 'common law' is called and 'adult interdependent relationship'. This required you to be interdependent with the other party. So I don't think saying that living in an apartment with other people for over three years would constitute that. Sure, it could constitute that, but it isn't just an automatic thing after living in the same residence with anyone after 3 years, it requires shared "emotional and economic responsibilities", which I am pretty sure most roommates do not have. While provinces don't have the same hurdles that the CIC does have, but I am pretty sure if your roommate decided to move out after 3+ years you would not necessarily have to go through a divorce-like separation...