I applied to a few schools last year with a <30 MCAT, and got interviewed and accepted by one and interviewed and waitlisted at the other. Ultimately I got a rejection letter in June from the school I was waitlisted at. When I got my April score back, which was 35+, I sent it to them anyway, and they re-reviewed me and accepted me in July. I think this is a really rare phenomenon though, and I fully expected to be reapplying this year (which I am anyway, since I am deferred openly at one school and couldn't move so last minute to the other school). Also, the new MCAT score really opened doors for me in terms of which schools I would be a competitive candidate at, so I was ok with reapplying. This process is crazy though. The school that interviewed/waitlisted/rejected/accepted me last cycle has been interviewing since September and just recently sent me an interview invitation. I mean, I was accepted there last year...
I would say don't count on it, but it is not impossible.
Treg