Thanks fietsbob, I just looked at a video review, and there appears to be plenty of clearance on the fork, but couldn't tell anything about the stays, but I'm thinking if it's built around a 42 tire width (and with all the extra clearance I saw on the fork), something like a 1.75" mtn tire would probably clear ok. (this is all still academic at this point, I'm not ordering anything till I've picked up the bike, and can see how much clearance there is.)
One more thing, I assume there's no hub-width issue to be concerned about?