Well, on my part of our railroad (UP) we don't use this system anymore.We call it Mobiltel. I asked our radio man the other day when I got to thinking about it and he told me that he had been instructed to go out and remove all the radio equipment which broadcast this service. Mobiltel is no more.
We had two separate mobil-telephone systems and it was programmed in the radios as such: Exec MT and MofW MT. 94-12 for the former and 61-33 for the later. Train crews used MofW and if I remember right, we would have to try about 6 different access codes as our train progressed thru the length of the system to get to the away from home terminal. We started out with *17 at home and by the end of the trip we'd have to use *23 to get it to ring up.
After cell phones came into vogue, it was funny when a new hire would take a trip with you and you'd tone up mobiltel and get a dial tone and their ears would perk up as you dialed out to someone. "How in the heck did you get that on there?" When I'd call a friend on their personal phone, the first thing I'd always tell them is "don't cuss", and tell them why.
But, I bet I haven't heard or used mobiltel in at least 5 years. Everyone uses cell phones. No self respecting official is gonna discuss his weed-weasel plans over the air for others to hear.
Our section men used mobiltel a lot. They would dial it up on their radios and would then put the radio output on the external loudspeaker. Whatever it was that they did would basically have an open line that they all monitored and if anyone, anywhere on our part of the system wanted to contact them, they'd key their mic and holler for them and the caller would wait for the callee to run to the truck and answer the call. Those gangs would be way to far apart for the radio signal itself to reach, so it had to be the mobiltel. I remember asking them how they did that, but I can't remember what process he described.
Anyway, they don't do that anymore. Cell phones have taken over for long distance communication.
On edit: I know original post is old, but as far as where the OP would find the access codes, I believe our UP timetable listed both the codes and the radio freqs. for your particular part of the system. When I first started, the old head conductors did lots of paperwork stuff over the radio on mobiltel, and as you progressed in your job they'd let you in on what access codes worked where and you'd write it down on your cheat sheets. I still have mine.