Amtrak trains, technically, have free onboard wi-fi. It's practically unusable because of how slow it is, particular when the trains are crowded, but sure... it exists. On my last commute from New York to Boston on the Amtrak Northeast Corridor service, I asked the conductor if there were plans to upgrade the service. While he shrugged, clearly having heard the question a million times before, Amtrak corporate was paying attention.
Amtrak officials announced that, starting with the Northeast Corridor, they will be upgrading their wi-fi. They plan on bringing speeds from the current 10Mbps (though I don't believe it was ever that fast) to 25Mbps. Amtrak has an opportunity open for a "Trackside Wifi Solution Sourcing Event." They are accepting bids for a proof-of-concept project, "results of the test project will be used to determine whether it is technically and financially feasible to construct such a network along the entire 457-mile NEC."
Lenetta McCampbell, Amtrak's senior director of passenger experience, said "the proof of concept design and construction could be complete by year’s end." Considering how well known Amtrak is for their delays, we wouldn't hold our breath, but are glad the gears are shifting towards usable wi-fi. All those writers-in-residence will need some way to procrastinate.