I checked their coverage map found
here
They specifically do not include NH, eastern Ct, WV, etc.
If you look at the Maine map, you can see some 'leakage' of the map into the state of NH. Not sure why they don't choose to include these states. Perhaps they cant reach agreements with carriers in those areas.
There coverage looks mainly to cover the major travel routes, (take a look at ME and VT for example), vaguely reminiscent of Sprint/Nextel. Wonder whose system they use?