Thanks for the replies

. My mom was a bit worried about the rides that have 'moving sidewalks' leading up to them - like Spaceship Earth and Haunted Mansion. She thought she'd take her cane to walk the lines, and see if they'd stop the ride for her to board. I'll let her know what I found out here
If she uses the wheelchair in line, they will board her at the accessible boarding area. They should also do the same with a cane. Just seeing a wheelchair or cane should clue the CMs in to the need.
For the attractions with moving walkways, the accessible boarding area is at the exit (usually, you wait in the Mainstream Line until just before the 'regular' boarding area. At that point there is a wheelchair bypass in order to get to the accessible boarding area.
This also happens on attractions where the boarding area is at one side of the track and the exit is on the opposite side. In order to get the wheelchair/
ECV on the correct side of the track for the exit, those rides also board at the exit.
I know they can stop those two if needed. The other ones with belts are TTA(which also has a steep incline), Peter Pan, and Buzz Lightyear, but I don't remember if they stop them. I guess they would have to if you couldn't get on the ride. I would ask before getting to close to turn back. Pirates has an incline people mover at the end, but when you take a wheelchair in, you leave by elevator. The thing you have to really watch out for is the end of the belt. That's the hardest part. We have had a couple of pile-ups with the people behind us because it takes my cousin so long to get off the belt.

I've learned my lesson. I get off first.
Peter Pan and
TTA have moving walkways and can NOT be slowed or stopped, except for emergency stops. TTA has a steep moving ramp to get to/from the 2nd floor loading area and it also has a moving walkway for getting on and off the ride.
Buzz Lightyear, Spaceship Earth, The Seas with Nemo and Friends, and Haunted Mansion have a moving walkway both as you are boarding and as you are getting off. They all can be slowed and stopped, but only when you board at the accessible boarding area. The CM at the regular boarding area does not have that control (you can explain what you need to the CM at the entrance to the ride). They usually will slow the moving walkway, rather than stopping it because that is usually enough for most people. They can stop those attractions if needed though - ask.
Pirates stops for loading and unloading, but has a moving ramp that goes up to ground level (you actually unload below the level of the stores/shops that the ride exits into). At the exit, the moving ramp is straight ahead. To avoid it, there is an elevator down a small hallway to the left of the moving ramp.