I'm also from Canada, but I have a very different experience from the other posts. I live in Quebec and speaking french as a primary language. I am still a CS student, but from what I have seen (I am involved a lot with other universities) the retention rate in Quebec is much higher. Only a minority is leaving Quebec for internships or jobs later on. Even if most of us speak perfectly fine english the culture is very different. I see very good people accepting 40-50k salaries for junior positions. Making a lot of money in Quebec is kind of taboo, so seeking a high salary is not well seen.
Last thing, our education system is basically free (1600 CAD per semester). After 3 years of university most of people in CS have at least 10-12k in their savings already.
If someone has numbers for Quebec only, I would not be surprised too see the emigration isn't really an issue.