I drive into Boston frequently from RI, and I find I get 4G about a mile before the tunnel on the Expressway (of course, sitting in Boston traffic lets me do things like that...!).
I live just outside Providence, and I actually got a 4G signal downtown for about 2 minutes... by the time I closed my mouth and tried to test it, the signal was gone...
4G is so close... but so far....
Ken