The May 2011 edition of RAILFAN & RAILROAD reported that MBTA "has leased five former (MARC) GP40WH-2s from MotivePower, Inc." The units are ex-MARC 52, 59, 60, 61 and 67. "Rebuilt from GP40s using wide-nose cabs taken from scrapped Burlington Northern F45s by MPI predecessor Morrison-Knudsen in 1994, the units had been traded in on MARC MP-36-3C's Nos. 10-35."
There are pics of them if you google MBTA
I was up there in Boston and just missed the event where they unveiled the locomotives at North Station. From what I've heard, they accepted three into service, one is being used for parts, and the other was rejected and sent back to MPI.