If NJT is restricted from running on federal railroads, theoretically that could also mean that the entire NJT Northeast Corridor Line gets shut down. Many stations in big towns/cities not or infrequently served by Amtrak such as Secaucus, Edison, Elizabeth, New Brunswick, and Princeton Junction would lose most if not all train service. There would be little reason to run the Dinky as well due to Princeton Junction having little service, so that will get suspended too. The RVL (beyond Bridgewater), NJCL (beyond Long Branch), and ACRL will not have access to a reasonable terminal station, and those lines could get shut down indefinitely too. Only trains that can access Hoboken without going via Amtrak will still operate. And to top it all off NJT will not only lose access to Amtrak's Sunnyside Yard, but trains at their Morriville yard will become trapped. All in all NJT's network will be a completely fragmented mess without Amtrak's tracks.
Train systems ridden (excl. airport trains): Amtrak, CTA Loop, D.C. Metro, JR (Central, East, West), Keisei, M&Erie, NJ Transit (NLR & HBLR), NYC Subway, Osaka City Subway, PATH, Shizutetsu, TDR Monorail, Tokyo Metro, TTC Metro/Streetcar