Talgos can't be used on the route now. NJ Transit has built a few high platforms on the former all-low E-L territory (their "Hoboken Divison"). If a service like this were to start up, it can't skip stations like Newark (Broad Street) or Dover in New Jersey, assuming the Lackawanna route, and there's high platforms at stations like Secaucus and Paterson on the Erie routes. (The Lackawanna did try out the
ACF Talgo in the 50s, but that didn't get off the ground.)
BTW, the bus was mentioned earlier in the thread. I checked the ShortLine timetable and it shows a 3½-hour trip for an average speed of 55 mph, which is kinda unusual for a highway bus with a number of stops, and really difficult to impossible in traffic (maybe even overly optimistic; there's a lot of traffic in NJ, especially at interchanges and tunnel entrances). This old
Phoebe Snow timetable shows a trip time of almost 4½ hours, which is an average speed of 43 mph (almost equal distance in spite of different routes); but there are a bunch of stops in New Jersey and the Poconos that an Amtrak train wouldn't stop at today (Brick Church, Summit, Blairstown, Cresco, Pocono Summit), so it wouldn't be a stretch to maintain enough of politically-expedient station stops and get the average speed up to 55 mph.