Yes - I ran RR in '06 - I spent some time talking to his neighbor (I think way down the road) that was there and he ran a Scout II that was very cool.
Exceptions are made from time to time at the discretion of Bruce Fowler is in charge of the whole thing. There was a guy there with a Jeep this year and he was allowed because Bruce knew him personally. In 2006 there was an exception or two for VTXS because they did a lot of trail cutting and maintenance. That's how that works. You can say that it is a Rover event, but there are always a couple vehicles that aren't.