they will if they can, but some of the larger or less manouverable ones won't fit (some can't turn sharply enough to get into the train car). Most of the strollers being used as wheelchairs are no bigger than a wheelchair and will fit just fine.
It has to do with the size of the ECV. The ones rented from parks are humungous compared to the smaller fold and go types or even the ones you rent from Randy's and Walkers. If the ECV is too wide or long the they cannot let it on the train. I have driven ECVs at various amusement parks and stores but the Disney ones are very large compared to others.
