We enjoyed similar pixie dust from a driver one evening, when we were trying to get to an ADR at the Animal Kingdom Lodge. We hopped a late bus to Animal Kingdom, figuring we'd get a resort bus from there. The driver said to us, "You know the park's closed, right?" and we explained our plan to him. He told us to sit tight and drove us right to AKL! We were so grateful!
@BeachPrincess - In general, we've had very good experiences with the busses at Pop Century. I haven't stayed at the All Stars, though. While you can't ever be assured of catching a bus right at six thirty, they do seem to run quite regularly in the morning. (Though it can be a bit frustrating waiting 15 or 20 minutes for a bus to your park, while six half-full busses to Magic Kingdom sail by.) I'd think if you're at the stop by 7:30-7:45am, you should get there in plenty of time. Barring acts of mis-transportation, that is.
If you've waited half an hour and find yourself getting nervous, you can call for a cab at the front desk. Also, guest services can alert them that you're running late for your tour.
There's actually a wee bit of leeway with that 8:45 tour check in. They will wait a few minutes for you, if they know you're on the way. We've done a couple Epcot tours, and we've always waited 15 minutes or so for stragglers. They know how hard it can be to get around the parks and they'll try their best to accommodate you. In one case, a very nice couple joined up with our tour about forty minutes in. A cast member brought them to us.
