Great question! I have always isolated fire/life/safety wiring from everything else, but I don't know the nfpa reference for that practice. I suspect that there might be something in nfpa 72, (National Fire Alarm Code), that might explain how these cabling separations might be required. I don't really know what the situation is in the case you described. It might just come down to a matter of separating class 3 cable from class 2 cable -- NEC 725.