http://trn.trains.com/news/news-wire/2015/09/08-stb-ptc
This makes this interesting. FRA has threatened to fine the railroads beginning January 1st for not having PTC, Congress doesn't seem to be making any effort to extend the deadline, the railroads have invested billions in PTC and related signal system upgrades - yet at best the railroads are only 1/3-2/3 through with their installations, and less than 1/3 of commuter lines will meet the deadline.
It looks like the STB opened the door for the railroads to embargo any haz mat, Amtrak or commuter operations from line segments until PTC is completed. The alternative would be for railroads to raise rates to pay the FRA fines, making certain commodities uneconomical to ship by rail. You don't think this will cause some nasty phone calls from certain rail customers to their congressional delegation?