Sonic,
Perhaps it's just a "style" thing. Obviously all musicians have their own unique style, and the great one's are constantly developing their own. But it just seems like once you can "master" another guys "style, it makes it much easier to learn their chops.
When I used to play my bass pretty heavily, it always helped to study a guys licks. Once you get it down, a lot of thier stuff follows the same patterns. Geezer Butler was one in particular. He used a lot of the same stuff on songs like Paranoid as he did on the later stuff he did with them.
Maybe I'm just stating the obvious here, just thought I'd point it out.
Randy