I think the reason you always see the P32AC-DM's in Conn. and NY because they have 3rd rail capabilities and since there is mostly electric passenger service there thats why yo see them mostly there.
Well, any train that operates beyond the electrified tracks need either P32AC-DMs or FL-9s to get in and out of GCT, or Penn Station in the case of Amtrak Empire Service trains. ConnDOT SLE trains can get away with using GP-40s because they only operate between New Haven and New London. Dual mode locos can only operate off 3rd rail, not caternary. The only 3rd rail zones in the northeast are on the approaches to GCT and Penn and on some Metro North lines north of the city.