The real difference is that the bureau is intended legislatively to govern markets that are already competitive. The CRTC is there to take a market that was a monopoly and transition it to competition. That implies a whole different view of things compared to when you're looking at the possibility of anti-competitive behaviour in an already competitive market. That's why the bureau is really not geared to help facilitate the emergence of competition. It's just there to protect egregious infractions.
On February 7th, 2007. See this statement in context.