Actually, its not uncommon lately for Shortlines to take a serious look at the benefits of trunking technology. There are a few roads that use LTR or Smartrunk systems in the southern states. However, the Union Pacific has a wide-area, Project 25 TRS up and running in Portland, Oregon area. Overall, U.P. officials have been very happy with the overall results. Likewise, Norfolk Southern has experimented with P-25 Trunking in Birmingham, Alabama.
I can see where a large rail yard could benefit from a TRS. This would allow for better frequency management, while allowing many different users access to the system at the same time. This would place hump operations on one talkgroup, while police, switching, repair services, and others can use stay on different talkgroups. However, each radio would be able to switch back and forth between them, allowing for better interoperability.
IMHO, I would look for more railway companies to migrate to Project 25 conventional, before they switch to a trunking system. With the mandated narrowbanding by the FRA and FCC coming up in a few years, I would look for more roads to make the switchover. In fact, BNSF, NS, and some CSXT licenses have been upgraded to digital voice and data modes for future migration to the newer technology, which will render older radios and scanners obsolete in the future.
73's
Ron