I would say the flights from HKG, LHR, AMS and YYZ would have the most international mix as these are large catchment hubs for a major airline. For example, CX funnels most transit passengers through their hub in Hong Kong. Similarly, Heathrow and Schipol are major transit hubs.
Having said that, I've taken CX from HKG to YVR numerous times, and it appears to be mainly Canadians on business or Hong Kongers (or ex-HKers who have moved to Canada) on personal visits with a sprinkling of people from PR China, the Philippines, India and elsewhere. Similarly, when I took BA from Heathrow to YVR a few summers ago, it seemed to be mainly Brits visiting on holiday, so anecdotally at least, it would seem that for most airlines, their home market makes up the majority of passengers. I've no stats to back that up, though...
On another note, finally some good news in the midst of all the route cutbacks at YVR by Air Canada. In March, Philippine Airlines is set to go daily from Manila and Korean Air will go daily from Seoul (source: airlineroute.blogspot.com).