Although this may have changed. This is an experience we had getting to e-ride night in 11/99 which was from 8pm to 11pm.
We went to the Studios that morning, then went to the resort for our afternoon break.
At about 7pm we were at the bus stop waiting for a bus to Magic Kingdom from All-Star Music. By 7:45 pm a bus still had not stopped at the Magic Kingdom stop. However, there were several busses marked "Special" that were dropping off folks from the Magic Kingdom, but not taking anyone back.
I finally went in and talked to guest services at All-Stars and got the reply that Magic Kingdom was closing at 8 and I informed them about e-ride night and they acted like they knew nothing about it. Finally, a bus pulled up to the stop and asked where we wanted to go and once again told us that MK closed at 8 and we informed him of e-ride night. He took us himself.
In subsequent e-ride nights we have attended, we have made sure to go back to MK at least two hours before e-ride night begins.
As I said, they may have improved this situation tremendously since then, but you might want to be aware that the parks seem to go into closing mode about 1 hour before closing and it might be hard to get a bus ride in the opposite direction of normal flow.
Carol