I was going to be a wise guy and tell you that they all use the same buses as all the WDW resorts.
But, I won't.
OKW buses are strictly for OKW. SSR, the same. I haven't had any problems with the bus transportation at these resorts.
VWL has boat transportation to MK (might also have bus transportation), plus buses to the other parks. We didn't use the buses here; we drove our car or took the boat to MK.
BCV and BWV have boat transportation to Epcot and Disney Studios (plus you can walk from/to these resorts and parks) and buses that they share with the other Epcot resorts to the other parks. Lots of waiting in the past, may be better now. Sometimes during the day they split up the resorts and buses and not all share one bus (Swan, Dolphin, YC, BC, BCV, BWV, BWI).