These problems are easily solved. 1) The right type of USB is the old, standard USB type A connector. Whatever kind of device you have, you should have a cabl

These problems are easily solved. 1) The right type of USB is the old, standard USB type A connector. Whatever kind of device you have, you should have a cable which plugs into this connector. The other USB connectors are on the device side; every charger these days has a USB-A connector on the charger side. 2) It should be pretty easy to design such a thing to be robust: all you have to do is make the USB connectors on the train easily replaceable. This can be done by putting the USB-A connectors on their own PCB, with all the charging electronics on a separate board below it. Then the supplier just needs to sell these replacement boards really cheap (because they're just a few type-A connectors plus a pin header strip) in bulk to the MTA. Even better, the MTA should get the design files, so they can farm out production of replacement boards if the supplier goes bust or they want to get a better price. Keep the charging circuitry on the lower board, and make the upper board easily replaceable with a screwdriver (with a security key) so maintenance workers can swap them out as necessary.