The majority of the costs of passenger rail is in the land-costs of placing those statins (and rail-lines) somewhere important.

The US Freight Rail network is just the right place to deploy this technology right now. We may have crappy passenger systems, but our freight is world class.

EDIT: It should be noted that PTC sensors cost $50,000 per train. But each train costs $2+ million, so the PTC sensors aren't that much compared to the overall system. The idea of having a similar suite of $50,000+ sensors / radios on every car is clearly too costly in contrast.