I'm pretty sure that there is interest in Pennsylvania in restoring the cutoff and creating an improved commuter route to NYC from their northeastern precincts; the prospect of improving the corridor through to Scranton would also appeal, at least from the point of view of Pocano tourism, if not for the sake of their even longer distance commuters to NYC. I believe that there is already a NJ/PA interstate compact which includes this project as one of their goals.
I's be surprised if NY were not interested in tacking onto such a line if it already was going to Scranton, just for the sake of adding Binghamton to the network. Moral support, for sure; votes in Congress, certainly; real money, perhaps a little.
Except for the Binghamton thing, NJ gets about as much out of this as NY does, which is to say, not that much - improved transportation for outside workers coming into the NYC area (at least some of them probably work in Jersey City or other NJ locations). There are not many more NJ commuter/residents left on the rest of the line to be restored in NJ, so they and NY are down to whatever people from the NYC area might want to go to PA or the Southern Tier. Connecting Binghamton should be a reasonably important thing in NY politics, but who knows how many budget dollars it might be worth.
Should such a route be created, would having the 3 states involved oblige Amtrak to participate, or does it have to go much further to qualify? Did the Phoebe Snow officially go all the way to Chicago, or was it considered two separate trains?
So, for this Binghamton thing at least to happen, PA in particular, and to some extent NY, need to either pony up some dollars to add to whatever NJ might be willing to spend, and they need to work together politically to get more federal dollars to help restore the cutoff.