Let me preface this by saying that I'm on the Worcester School Committee, so I am not going to pretend to be unbiased.
It may be useful for your cousin to know (as you're discovering) that Massachusetts school districts are much, much smaller than California districts and much, much more segregated by district than California districts. Our suburbs tend to be much whiter; much of our diversity (not all of it, but much of it) is in our cities.
Because of the relative size, there are programs for students (autism or otherwise) in some of the cities that smaller districts don't have the capacity to run. That is not universal, but note that many smaller districts will send students with special needs (depending on the level of need) to schools that are not district-run schools.
Worcester Public Schools does run a comprehensive program for our students who have autism. I have not experienced that as a parent; I do know of parents who speak of it highly.
If your cousin is intending to choose where to live based on the ability of the public school system to serve his son, I would strongly urge him to get in touch with families of students with similar needs within that district.