I have in front of me an FRA supplied flow chart showing where electroic and electrical devices are prohibited and a list of exceptions. Exception #4 is"Under authorized conditions of 49CFR220, may use RR supplied/authorized device in lieu of radio, to conduct train or switching operation." This allows a railroad supplied cell phone or a personal cell phone if sanctioned by the railroad's operating rules to be used for comunication during switching or train movmements. I believe if ones cell phone rang for a personal call under these circumstances one would be obliged to ignore it, and similarly refrain from making any personal calls. FRA requires a second means of communication in the cabs of locomotives which in my slim experience is usually a hand held radio in addtion to the mounted radio in the cab. On a local shortline here I recall being told they carried a satelite phone as a second means as radio was spotty in the canyons operated through. I presume if authorized by the railroad's operating rules a rr supplied or personal cell phone could satisfy this requirment for a second means of communication in addition to the a cab mounted radio. A large red foot note to the above mentioned flow chart " WHILE ON DUTY use of personal electronic/electrical devices for other than voice communication is prohibited except as noted above.