Good Evening,
My son , who is "classic autism" love the labels....... was non-verbal until age 6. He did not "pee" in the toilet until 7 years old and a BM didn't happen until 9. We were out of diapers fully at 10 and he still asks for Momma's help, but is really pretty good at bathroom skills , right down to washing hands. He will be 15 years old this year.
Toilet training, as everything else, with the young autistic child takes time, patience and bribery. I am happy to talk with you as it can't all be written in a little email response. Email with a phone number and I will give you a call.
I talk with many parents in a course of the day on a variety of subjects. The best help I have received is from other parents or caregivers who have the day to day, 24 hour / 7 day a week experience with raising a youngster with autism. There isn't an "expert" alive who can give better advise because frankly they don't live it or they NEVER understand living with autism.
Take Care,