A bit of creativity then, for if the NY tunnels were broken.
The big thing is NYP. If that's broken, then you have to move folks somewhere else. Going towards Boston, that's Grand Central. Going towards DC, you got to cross the river, and the only alternative now is PATH at 33rd and 6th going to Hoboken or transferring to Newark.
BOS to NYP, you can transfer to Metro North at New Haven, and the NEC will have a northern section it can run with the electrics.
WAS to NYP... is a bit more complicated.
- The easiest transfer point to Amtrak is Newark. Transferring at Hoboken I think will be hard, because I think the caternary is 60Hz, not 25Hz. Turning the train will require a diesel to move it down to the wye and back until they double-head the Regionals. Plus, every NJ Transit train will be redirected to Hoboken or terminated at Secacus Junction.
- To lighten the load, LDs would terminate at Washington or Philadelphia (Pennsylvanian and Keystones) and transfer to Regionals.