As a high school person, I don't understand what "alternative certification" means, really. I mean, is this different than the "alternative certification" we already have? Like, when we were starting Feinstein, I literally met a guy (Hi, Dominic) in the checkout line at Barnes and Noble and, based on the geeky book he was purchasing, ended up recruiting him to teach math at the school. He wasn't certified. He got emergency certification, started teaching immediately, took night classes, and as far as I know, he's still teaching (certified) in a well-regarded Providence charter school. And that's not an unusual anecdote at all, particularly for math.
In an MAT program, you'll probably have some kind of intensive summer session, than a full year or at least a semester of student teaching, which may end up meaning teaching full time. In an alternative certification program, you have some kind of intensive summer program, and then start teaching, with some ongoing mentorship. There isn't much difference, is there, except you're eased into things a bit more, and you're paying instead of being paid in a traditional program?
There's that, and a good contemporary "alternative certification" is prestigious, whereas a traditional program is not.
Am I missing something here?