One possibility is that they could be leased for a pilot (or semi-permanent) express commuter rail service from RI to Boston. That has been discussed between the states for some time, and this article mentions that Massachusetts was negotiating a lease with Amtrak for electric locomotives at the time: https://www.wbur.org/bostonomix/2019/08 ... mit-boston
Unclear what rolling stock would be used; perhaps the MBB coaches that are currently being refurbished? Implementing an electrified express train from RI would be a political win for RI politicians and would be a relatively easy-to-achieve milestone toward the T's goal of electrifying commuter rail (even if it would only be a subset of service on the Providence line).
The Montreal MR-90s would be a great choice for the "starter" Fairmount/Lynn electrification IF they meet FRA requirements and can economically have ACSES installed, until purpose-built equipment could be obtained.