Most of your class I freight railroad agents work alone. They normally take calls from a network operations call center part of the rail carrier. CSX calls theirs the PSCC. However, almost all special agents have radios programmed with their local and state systems with capabilities to run tags or call for back-up. Very rarely will you see these agents solely utilizing these radios unless they are working some sort of detail with a local agency. At which point most of those communications will be utilized on a interoperability TGID/frequency. CSX in the Tampa area will work details with Tampa PD to clear out homeless camps. They normally utilize ISSI5 so they can maintain communication with a local PD agency provided dispatcher. These agents will also utilize railroad AAR channels to communicate with train crews in the event of a emergency but, once again this is rare on your class I freight railroads. The RRPD channels in their railroad radios are most definitely full ENC.
On a day to day basis these agents are normally dealing with outside party dumping complaints, Homless camps, intermodal thefts or employee complaints/ethical complaints. Anytime the rail carrier causes property damage such as a train VS vehicle or even a fatality they will respond if they are close.
Hope this helps