MBTA could use them on the Providence Line no doubt, but do they really need them?
Let’s review their locomotive roster, and how many of them they need.
Per this Wiki article they need 58 train sets for today’s operations.
https://en.m.wikipedia.org/wiki/MBTA_Commuter_Rail" onclick="window.open(this.href);return false;
Here’s a listing of locomotive roster
40 HSP 46 by MPI
2 MP36PH-3C by MPI
12 F40PHM-2C by MK (*2003-2004*)
25 F40PH-2C by EMD (*2001-2003*)
25 GP40MC by GMD (*1997*)
The total is 104 diesel locomotives. Granted 42 of them are fairly new, leaving 62 reaching end of life, but all have been thoroughly *refurbished to extend their lives*. MBTA also has 3 other diesel locomotives not used in revenue services, being used for maintenance work trains.
Amtrak leased 15 HHP-8 and MARC bought 6 to add to their 4 AEM7s.
If MARC could operate the 40 miles between Baltimore and D.C. with 10 electric locomotives, I think MBTA could operate the 43 miles between Boston and Providence with 15.