From my understanding, the program is only six years for students who graduate from a select few dental schools ie. those whose dental students go to basic and clinical science courses with the medical students at that school. I can't remember which ones but I think it is like Harvard, Columbia,...(I'm sure someone else on SDN knows).
If you are in the six year track, you attend med school years at UCSF.
For all others accepted to the program, it is a seven year program. The residents have to do three years of med school. It is my understanding that if this is the case, the residents are at UC Davis during that time.
Hope I am accurate. Please correct me if I am misunderstanding as well.