> But that cost is what the railroads don't want to pay, as they could also do the same thing by hiring more employees (and have some percentage of them "idling" at any given time).

At one point the article mentions "on call" (the correct term is "Extra List") and that's exactly what you describe. You'd have say an engineer, who may be new and has no regular assignment - he'd put in his early months or years "on call." The company can call him at any time, and say "get to XXX, your train will be there." The whole issue is having enough to cover shortages.