This is locally-supported 40B, which is basically a way for rich white suburbanites to dump affordable housing in places they don't have to see it. In some cases that's okay (if there's convenient transit, for example) but in this case William Street is an access nightmare with egress only to WB Route 9 (which can't really take the new cars from this development). As we discussed in the other thread, there's an intriguing transit accessibility for this via Waban if a footbridge were built to Newton, but really MassDOT, the Town, and the developer need to extend William over 128 through the former Harvard Pilgrim property if anything more is built on it. In a perfect world, the Harvard Pilgrim site itself would be densified and the entire William Street corridor returned to a forest area to front the river, but that's obviously not realistic.
You could walk to Eliot. It's a mile so it's rather long. I've been to this Office Park driving and yes it is a nightmare getting there.