This seems to imply that there are separate servers running for Canadians accessing Facebook, so at a minimum, that would give some leverage into forcing them to follow Canada's rules. Now, if those servers are physically located in Canada (no, I haven't bothered doing a traceroute to find out where fbcdn.net ends up), that would definitely force them to follow those rules.
Slightly OT, but in my current job and we recently went looking for a new hosting company to host our database (which has a fair amount of private data in it). Because my company gets a large amount of our budget for the federal and provincial governments (it's a non-profit) we like to abide by as many of the federal government rules when it comes to IT and data privacy. One of those rules is any private data must only be hosted in Canada and it can not leave the country. A few companies came to us as "the Canadian branch of hosting company X". The conversations went like this:
Me: Where are your datacenters?
Them: We have them all over the world.
Me: Ok, but in which of those datacenters is our data going to be physically hosted?
Them: We can do distributed hosting so it's in many different datacenters
Me: Yes or no, Are these datacenters in Canadian territory?
Me: So, I'll take that as a no, which means that you know we can't host with you because of the government ruling about hosting private data outside the country.
More and more Canadian companies are taking the approach of hosting only in Canada, if only to ensure that they know the rules for data privacy and know there won't be a conflict between Canada's and the other country's.