I know Purdue ran cover 2 and it was effective with a pretty thin talent pool. I'm not knowledgeable enough to break down all the finite x and o details, but what I do know is that the version they ran counted on pressuring the quarterback and the back field. Then the safeties make noise in the secondary and capitalize on rushed passes. The most important factor in that defense was speed over size, and since they were not a powerhouse school they were not going to consistently get guys with both speed and size. However, with that limited talent (they would have maybe one or two NFL calibur guys on the defense) they were able to be close to the top of the Big Ten in defense every year in the late nineties and early 2000's.
With Tennessee having a good recruiting base to get those guys, and with Kiffin's "Tampa 2", I really think the Vol Defense has the potential to be legendary. The only downside will be that some cover 2 styles are "bend but don't break," and after watching soft defenses for so long, I'm not sure if the Vol fan base will handle that very well.