I know I'm a couple years late on this news, but ATCS (Advanced Train Control System) radio relay that replaced pole based code lines for Centralized Traffic Control schemes is in the process of changing frequencies (or just being completely phased out) due to an FCC directive that will reallocate its 900Mhz spectrum for wireless broadband in 2025. For the last 20+ years ATCS has been super useful for enthusiasts to monitor railroad dispatching in real time as data packets are relayed from station to station, just like with an old CTC code line, only now they can be sniffed and displayed.
Although some railroads like CSX shifted away from ATCS in favor of satellite links years ago and hard links like fiber optics were popular for a window in the 80's and 90's, ATCS has been a massively useful took for those looking to take photos of trains or just gather data that can be used for all manner of public policy. Word is that for those railroads wanting to keep the ATCS system, the data will piggyback on the frequencies allocated for PTC communications. However because the PTC communications specifications have to be purchased for a sizable amount of money (who'd have thunk it), the ATCS monitoring community is facing a reverse engineering challenge.
The silver lining could be that after some amount of outage, the community will be able to monitor not only lineups, but also PTC signaling and authority information.
