Not to be confrontational, Steve, but...
To me, the question whether Canadian Content regulations have "springboarded some people into international stardom" is not very relevant, since I've noticed that people who go on to achieve that exalted state mostly cease making music that has anything to say to me. To my mind, the purpose of CanCon is to help Canadian musicians to make a decent living while remaining in Canada and possibly making music that is relevant to Canadians. And I think it does that.
I'm talking about "stardom" in the quasi-pop field, not the folk field, as folk music enthusiasts tend to be willing to embrace music from cultures other than their own. So a folk musician can become an "international star" in the folk world (whatever level of income this implies -- not on a par with Céline Dion's, I guess...) without having to abandon their cultural identity in their music.
I'd like to hear Canadian working musicians comment on this -- anybody listening?