Sen. Charles Schumer is pushing the Long Island Railroad (LIRR) to get Internet service on board: Unfortunately, the numbers thrown out ($1,000 per train car) are nothing like the cost unless each train car simply had a cell gateway stapled on top. That cost would exclude installation, maintenance, bandwidth, and network operations. The railroad will issue an RFP later this year.
Also, in this Newsday piece and elsewhere, Sen. Schumer seems to think that there are similar and inexpensive systems running all over the U.S. There are now a number of production systems in the U.S. (and elsewhere) on trains, but there isn't anything running on the scale of LIRR. The closest is the MTBA (Massachusetts Bay Transportation Authority), which is either in the process of or finished with a rollout across 13 commuter lines after a successful test on a Worcester line.
Other rail-Fi projects are much smaller in scale, often involving (as in Utah and elsewhere) new projects that were designed from the start to have Internet service in stations and on board.
In the Bay Area, the BART system has a contractor in place (Wi-Fi Rail) which is ostensibly in the process of setting up systemwide Internet access as we speak. If Wi0Fi Rail is successful as it rolls out in the Bay Area, it's likely that the company's approach will be useful in other metro areas that are otherwise quite expensive to get backhaul and signals through.