I have both Amateur (ham) and GMRS licenses and often carry a handheld radio (HT) when railfanning. There are no established frequencies for radio communications. But these are my suggestions if you're chasing in a group:
Amateur: 146.490 MHz
147.540 MHz
GMRS: Channel 4 - 462.6375 MHz. This channel is available on both GMRS and the low power FRS radios.
GMRS: Channel 16 - 462.5750 is used by many Off-Road groups (Channel 16 is 4x4...)
I prefer to use a dedicated scanner whenever possible. I do, however, program a few of the more active Road Channels in my radios. Just in case.
Programming all the AAR frequencies in your HT is a chore. But if your radio is supported by CHIRP it's a breeze to import them.
Photo: Baofeng UV5R mini