I don't see why they couldn't. You could just leave out one or two rows of seats and have plenty of room for a wheelchair, also extra luggage and package (if no wheelchair was onboard). You could have that in maybe one car out of five or ten, given that a new car arrives every thirty seconds.
From the pictures it looks like able-bodied passengers don't sit upright, so a person in a wheelchair wouldn't fit. Perhaps they could be helped into a seat and then helped out, though.
Serious question BTW, I'm not sure what exactly ADA mandates.
