I was listening to Driven on the Different Stages Live CD and I was wondering if a) is that his jazz bass and b) is he using some kind of distortion to achieve his growly sound?
Yes. He uses a SansAmp Bass Driver DI, and some other stuff. If you do a search, you'll find links to Geddy's gear throughout the ages. The only period it didn't cover (last I saw) was the latest: One Little Victory.