The interview day is long but very informative. You spend a few hours at the actual medical school for info sessions and TBL, then take a bus out to Beaumont-Royal Oak (their clinical campus) for a tour, lunch, and interviews. At the end of the day you are bused back to the med school campus where there is an optional tour (which I recommend - this is the only chance you have to see the lecture halls, student lounges, anatomy lab, etc.). There are lots of chances to talk with current students.
There are two interviews that are typically one-on-one with faculty/staff or a physician in the Beaumont system. I'm pretty sure the dean said that some people may be interviewed by an M4 student and a faculty/staff/physician together. My interviewers each had an identical set of questions they were "supposed to ask" and then both had some different questions they wanted to ask me, some being fairly standard interview questions, others based on my specific application. You'll get an idea of the type of people they want in their community during the info session at the beginning of the day - they seem to really value active learning, collaboration, and well-roundedness. If you check the SDN interview feedback for Oakland, the reviews there (although there are only a few) were fairly accurate based on my experience!
They said we are not evaluated during the TBL exercise, and all the admissions people left the room for it (it was just the interviewees and a professor). It seems like it's just to show you what the learning environment is like.