"For mass transit, that is, for PUBLIC transportation, the use of tax dollars is the only sensible way to create a commuter rail network."

Taxpayers being forced to pay for 150-year-old technology is the ONLY way to create a rail network.  In some respects it doesn't matter who pays for it; it will be a failure by all measures.  A better collective transit system is the Flatiron Flyer i.e., bus rapid transit.  Buses are infinitely more flexible for inevitable route changes, cost 1/10th as much when taking into account all costs e.g., capital and operating, and have the added benefit of allowing profit generating HOT lanes.