I have all the band channel freqs listed on the RR Freq page of my site, along with freqs for many individual railroads as well. The big railroads pretty much use every channel in the band, somewhere in the country. The smaller roads use 1 to 10 channels or so, depending on their size.
Railroad comms are basically broken into the road channels, where trains talk to the dispatchers... Yard channels, where switch crews talk while switching cars... And then other various support freqs for intermodal terminal ops, maint., maintenance, and other things.
Dave
-DPD Productions - Featuring the NEW TrainTenna LP Gain RR Scanner Antenna-
http://eje.railfan.net/dpdp/