There is no pre-set grouping of resorts. Of course they like to group them geographically, and they do it that way when they have a lot of people going to all the resorts.
But if at the time you arrive there's no one else going to any of the Magic Kingdom area resorts, Contemporary will share a bus with other random resorts. It can happen.
In most cases, there is no pre-set order of drop-offs. In most cases, the driver makes the decision on the order.
The ONLY exception to the above takes place in the Magic Kingdom area resorts. The only time Disney plays favorites is with Grand Floridian. The drivers are instructed to drop off GF guests first.
BUT ...
If there are also Polynesian guests on that bus, they MUST drop off first at Poly and then GF. They're not playing favorites with Poly, it's a matter of logistics. The only way to drive to or from GF is to pass by Poly. If a large bus is driving from GF and wants to turn into the Poly complex, the bus will be unable to make that tight left turn without stopping, backing up and then completing the turn (a manuever commonly known as a "K-turn"). Well, for obvious reasons, it's not OK for a bus to make a K-turn in the middle of a street. THAT is why any bus going to both GF and Poly on the same trip MUST stop at Poly first.
