Is it conductors, or just conductors in the cab? I would doubt that conductors back walking through the cars have a big effect on the outcome of an incident or calling signals and whatnot.
Actually a conductor walking through the cars can still have a very big effect on the outcome of an incident. I'll cite one example where a distracted conductor could be the difference between a fatal accident and avoiding one. Please note that this accident had nothing to do with cell phone use, but it does provide an example of how a conductor could easily be the difference between life and death.
Several years ago there was a fatal collision between a MARC commuter train and the Capitol Limited. The MARC train was running inbound or east to DC, while the Capitol was headed for Chicago or running west. As is often typical on many roads, inbound trains run on the southern most track and outbound typically on the north track. However, the dispatcher had routed the Capitol onto the southern track in an effort to leap frog him around a slower freight train. The Capitol was to cross back over to the northern track after clearing the freight train.
Meanwhile the MARC train approaching a station stop, received an approach signal before the actual station stop, warning him that the next signal he would encounter would be a red or stop signal. The MARC engineer made the station stop, but then apparently forgot that he had just received that approach or slow signal as he left the station. So he accelerated to track speed, instead of running at 20 MPH prepared to stop at the next signal. As a result, by the time the red signal was visible to him, he was already running at a speed that ensured that he would be unable to stop prior to that signal. Despite applying the brakes to slow the train a bit, he nonetheless passed the red signal and ran right into the side of the Capitol Limited that was crossing over the switch at that moment to reach the northern track. The MARC engineer, along with several passengers lost his life in that collision.
At the moment I don't recall if signal calling was required at the time of the accident, although I believe that it was. In any event, out of this accident grew the rule Delayed In Block (DIB). This rule basically says that anytime a train stops along the way for any reason, unless the engineer can see the next signal at the moment that they start to move, they must proceed at a restricted speed, prepared to stop, until they can see the next signal.
So now if we replay this scenario once again, between signal calling and the DIB rule, any conductor paying attention is going to immediately radio the engineer to find out why he's moving so fast under these conditions. Failing to get an immediate response and a speed reduction, that conductor is going to be pulling the emergency brake in the car he/she is in. Whereas a distracted conductor is far less likely to notice that the engineer is going to fast for either the last signal or the DIB rule.
And that could well be the difference between disaster and a safe run.