I had a breakfast BOG reservation on Friday, December 4. Upon finishing breakfast at 8:30ish, we were led to form a line near the mine train. They let us into the Fastpass queue in time to get one ride in, perhaps at 8:50 or so. No earlier. By the time my family got off at 9, the regular line extended way back towards the tea cups, so there was no chance for a quick second ride.
Yes, that jives with our experience on Friday.