Our district has integrated preschools--about half the kids were on IEPs, and half were "regular" kids from the community. It was hard to tell who the "special ed" kids were, most of them seemed borderline. The more severely impaired kids were not in these integrated classrooms, for the most part. The big difference between them and "regular" preschools was the fact that the integrated classrooms had a lot more staff, like aides/paraprofessionals/special ed teachers. So that they could work with kids on the goals in the IEPs.
I hear what you're saying on play-based preschools, I think what you need is something that is highly structured, but does not force academics that are way too easy for a large part of the time. So if the preschool has learning centers with something that even an advanced child could enjoy, that would probably work well. The integrated preschools that my kids were in had a mandatory parent day where where parents were supposed to stay with their child and do the centers with them, sit with their child in circle time, etc. I think that helped the kids (even the typical ones) learn what was expected of them.
