i ran on the m&b back in late 2005, just after katrina. i ran the detour trains between the kcs in meridian and csxt in montgomery. the motley assortment of junkers there, was an interesting time. run through power was sweet. 8-10 sd-40's on a 200 car train of loads was a regular deal. i also ran the timber rock, mid 2004. we had a lot of potash traffic from the southwestern railroad using run through dp power. in a strange twist of fate, i went to the swrr, after i was done on the m&b.
back on topic, some radios are wired to the bus bar that runs the breaker panel. some have a switch that's attached to the battery switch, and you have to shove the knife switch all the way in, to hit the toggle that runs the radio. i've seen them hardwired, and once you pull everything, the radio is still on. i guess it depends on how under-qualified the people were, that worked on them. if you can't figure out a circuit, why not just run a new wire from where you want to start, to where you want to end. happens a lot more than you'd believe.
even class one guys can relate to the retards that can't fix an antenna wire, so they just stick a magnetic one somewhere on the cab, and leave 50 feet of coax hanging in the cab.