I visited the postbac office at UVA while I was doing summer research there. The full-time director was very personable and informative. At the time, she told me there was no linkage, but it seems like they do now, however limited. Postbacs take classes with undergrads, but they apparently get some leeway when it comes to finals and stuff. My friend who was an undergrad pre-med said the postbacs are very smart and hard-working. I contacted some of the students via email, and they got back to me with super long emails, gushing about how amazing the program is. Overall, it seems like a really good, new program with a lot of support from both the staff and professors. Charlottesville is a classic southern college town... lots of amusing traditions and school spirit.