I'm clearly not going to link to leaked content, but from what I've gleaned, I have made a 'guess' of the playable area.
This link is to a google map of Boston with a square superimposed showing the approximate play area.
https://dl.dropboxusercontent.com/u/87106516/bostonguess.png
We knew Lexington was covered so Salem now appears likely.
It correlates well with past guesses, though it now appears more of a square than a horizontal rectangle as many speculated.
Perhaps Bostonians will be able to comment on interesting real world locations at the margins...