They could use cellular modems (the locomotives already have one, normally) or LoRaWAN

The answer to a hyper-localized security issue isn’t attaching the equipment to an insecure network nor is it shifting to use insecure IoT type devices.

But $!

For that one guy.

Outweighs the safety of a nation.

Don’t you get it yet? You don’t live in a society, you live in capitalism.