I went to Michigan for dental school. We had a guy who started with my class that had finished his MD already. They sped up dental school to be only 3 years, and then another 3 of residency. During our summers he was in rotations to make up for some of the time through the first three years of dental school.
I remember he had said he interviewed at Penn and Alabama also, all three of which were willing to construct similar programs for him. I think it's not usually official, but programs are interested if applicants are. You probably have to contact them to get the ball rolling....