This NEC FY21-25 Capital Investment Plan is a pretty good source of information.
http://nec-commission.com/fy21-25-cip/s ... projects/
Wiring New London's track 6 is in here as Shore Line East Track & Catenary Improvements (FY 22), to start this spring and last a year, apparently fully funded to the tune of $10 million.
Platforming at New London on track 6 is already a challenge with the existing coaches, but I think it would be essentially similiar with an M8. I figure a bridge plate would be used to board and de-board the train via one door. With long dwells and low ridership at NLC for the foreseeable future, it shouldn't be much of a problem. Platform improvements are of course a need longer term at that station, but not a problem exclusive to SLE.
A meeting of the CT Commuter Rail Council last year seemed to demonstrate a real lack of enthusiasm for operating M8s on SLE. Among those present, it was only Jim Gildea who affirmed that the M8s should be used on the line, for thru-service to Stamford at the very least. One CDOT staffer's comments demonstrated an eagerness to get the testing over with and the whole project retired to the history books. I hope this attitude is changing in favor of a permanent transition to an electric fleet which would seem to be a better use of assets with numerous additional benefits.