Adding to the other reply .....
Since the time I originally wrote that, we have used the DME bus multiple times. Each time I have looked in the baggage area of the lift buses, there has been at least one wheelchair stored there. My guess is that all the buses with lifts have a wheelchair stored there.
Putting the
ECV under the bus should not be a problem as long as it is not too heavy (for example, some models do not come apart and weigh more then 100 pounds - too heavy to lift).
I have seen
ECVs under there for passengers who walked up the steps, so it can be done.
There may be other options if the ECV can't go under the bus and the ECV user just can't stand the idea of riding in it to go up the lift. For example, riding a wheelchair up, sending the empty wheelchair back down, then sending the empt ECV up on the lift and moving it off the lift in 'push' mode.