Just an update. We were at the parks last week, and did the BOG breakfast on Tuesday (June 21) and Saturday (June 25). Both days were 9 am park opens with the 'Early Morning Magic' option. We were able to order 2 kids meals for our family of 4 (DH and I don't eat breakfast) and leave our seats by 8:35. With a quick bathroom break, both days we were the second group in line for Mine Train. The line was held by a CM in Fantasyland costume. On the Tuesday, the CM waited for a manager (person with a Disney badge wearing 'business attire' instead of a costume) to come over and lead us into the line. On Saturday, the CM lead us to the start of the line at front gate rope drop, then waited for the manager to remove the final rope barring our way to let us in.
Both days we were led into the standby line, while early morning magic people were in the FP line. We were definitely ahead of the rope drop crowds from the front gate, but they were arriving as we were boarding the train. Both days we were able to leave the Mine Train and immediately run over to Peter Pan for a 15 minute wait (just long enough to enjoy the queue). After this, we were able to head into Frontierland/Adventureland for some very short waits until about 10:30 am.
Hope this information helps people who are considering the BOG breakfast!