If any of the old wiring were left in place, it most likely would have been in circuits that weren't being used and weren't carrying much current in any case. It's more likely, though, that the "locomotive mechanic" in question either wasn't really qualified to work on the electrical systems or he just thought he saw paper wiring; I seriously doubt BN electricians would've left old wiring like that in place on a unit being overhauled or converted to an RSPU.