BN or UP used to run a tank car loaded with diesel fuel in the middle of a 4 engine consist, but I think it was more for economy than operational needs. As I remember the fuel was less expensive in one part of the railroad than in other parts, so they would send the train out from where they had the cheap fuel with the locomotive tanks topped off and the tank car topped off, and then as they used fuel from the loco tanks, they would transfer in fuel from the tank car to get through the area where the fuel was more expensive until they could get back to where they got the cheaper fuel.
On a model railroad, I'm not sure refueling is an issue with modern power. I'm not sure how often the prototypes need to be refueled, but it is seldom enough that when UP bought SP, they were leaving trains idling on sidings waiting for crews to bring them in. Unfortunately, part of the problem they had was that the trains would be left on the siding for so long they would run out of fuel while idling. Restarting a diesel engine that has run out of fuel is not very easy either. I suspect, based on how long it took us to bleed off small diesels in transport refrigeration units that ran out of fuel and went airbound, that a four unit set of dieasels that ran out of fuel would probably take a mechanic 1 hour each unit at least to get them started after they got a fuel truck out to the siding to refuel the engines. Whether the U.P. was sending one mechanic to start all dead units in a consist, or if they sent a crew of mechanics to work on starting all units at the same time, I don't know. I would imagine they would send at least two men at a time, so that if there was an accident, there would be help available.