My son is not on the Autism Spectrum, but at the age of 17, he is non-verbal and functions at the 3- to 5-year-old cognitive range. He exhibits characteristics of Angelman Syndrome, but he has not been diagnosed. June 13 of this year was the last day he wore a diaper.
We are not out of the woods yet (after 27 days, he just had his first accident-free day) but he has made incredible progress, considering the fact that he had NEVER gone on the toilet before.
His school staff were actually the ones that pushed ME to get him trained and wrote in his IEP that toilet training takes priority over academics.
This has been the most intensive and difficult thing I have EVER done. I still do not have my life back yet, although things are starting to return to a sort of normalcy. The ONLY reason I have gotten this far is because of a nurse I am working with who has provided constant phone support and encouragement. She has six children of her own and has trained over 900 children, both typically developing and special needs. If you are interested in more info about Wendy (the only person I am aware of that works with toileting teenagers), send me an email at firstname.lastname@example.org.