Thats the funny part, there are none, although they threaten confiscation of the bike... based on an old "registration with your town" requirement no one does anymore... not the ordinance they say is about mt biking or bikes on the trails (which is actually only about roads, sidewalks, paths, and not blocking cars, and mentions neither mt biking nor the word trails-- besides predating the '95 mt bike ban which was created behind closed doors by over ten years... )
So there is far as I know, no posted penalty for mt biking, only for not having your bike registered in your town -- a separate issue and a moot one at that which no one requires anymore as we all know.
However, I do believe some riders said there was a fine for mtb-ing, not sure how much cause I don't think it;s posted anywhere.
The fliers they posted saying mt biking is forbidden only mention the threat of confiscation, which again is related to registration not mt biking one way or the other... although they quote the ordinance they say is about mt biking -- which doesn't mention confiscation... the whole thing is weird...