SLE will not see M8s for several years. Their stations have to be converted to high level platforms and the whole order must be completed as well. Also after this is complete, many tests will have to be done. So don't get excited after that so fast.
The M8s run on theses trains:
Weekday:
1511
1521
1340
1244
1451
1375 (arrives on Track 108 in GCT)
1570 (Track 109 in GCT)
1370 (Track 108 in GCT)
1387
1588
1595
1594
Weekend:
6509
6525
6329
6341
6550
6337*
And also:
The New Haven Yankee Clipper*
*M8s not guaranteed on trains with this mark.