Even if you go back to pre-Covid commuting patterns and percentages, it's misleading to state that they're profitable because the trains make more money then their operating costs. When you factor in the cost of equipment and rail (along with their maintenance) it's pretty tough to make a profit.
The MTA only breaks even on its transit operations, and that's because they massively overcharge for the bridges and tunnels under their control - that subsidy alone is billions of dollars. The Port Authority (NY/NJ) makes money on all of its properties (WTC, airports, ports, bridges, tunnels) yet still has to shell out (hundreds of millions) to cover losses on the tiny PATH system - which connects four densely-populated areas (Newark, Jersey City, Hoboken, and Manhattan).
The only rail system I've ever seen that's truly profitable still has an asterisk next to its name - Hong Kong's MTR system. The government granted them land around the stations for the MTR corporation to develop and operate. Their model (rail plus property) is demonstrably successful.
NJ Transit has bus and train lines that should be scrapped. As a government/political entity the “elected officials” will not allow it. As a private company it could make fiscally responsible decisions - which would cut out any line - bus or train - that cannot support itself from the fares
For NJT to make money for anyone they'd not only shred the labor contracts, but also the schedule - which would make the service far less useful. However, I do believe that they would lose less money if the management and operation of the system was turned over a different group that was compensated based on performance and free of political interference. Good luck seeing that happen in New Jersey. Most of these systems (especially the MTA) would benefit from such a change.
I grew up in New York City and I see the value of rail as a transport system for people - but like most of America, the funding model is broken. Their management and operation models are also broken.
While I am all for privatization, the sad reality is that you can't run trains with these labor contracts and schedule desires and make money on passengers alone. You need something else to absorb the losses. If the interstate highway system didn't massively cut into freight (train) revenue, there would likely be more privately-run passenger service today, along with more freight operators.
My comments do not, unlike your assumptions, assume either Amtrack or NJ Transit could be profitable as is.
My comments, unlike yours, do not pretend every single train or bus line in their systems could be profitable on their own if privatized.
Most cannot. However some could be.
If Amtrack was reduced to just the Northeast Corridor lines from Boston to D.C. and shorn of the rest of the system, and privatized, it could be a profitable concern.
If a similar scalpel was taken to NJ Transit as a private company, it too could survive without taxpayer subsidies.
Politics, not deep transportation analysis, props up the demand for the continuation of the most deficit causing parts of those systems.