All WDW busses should be able to accomodate 2
ECVs (scooters) or wheelchairs. Occasionally there will be a bus with a ramp or lift that does not work properly, and you'll need to wait for the next one...or there may already be two on board.
The
ECV/wheelchair parties will board first, through the back door of the bus. After the ECV is loaded and secured, ambulatory guests will load through the front door. ECVs unload last, after the ambulatory guests have exited the bus.