If a railroad locomotive is an iron horse, then a vast herd of them has been put out to pasture in Salt Lake City. They’re lined up, nose to tail, waiting to go nowhere — at least for now. By some estimates as many as 200 railroad engines — each one costing about $3 million — have been sidelined over the last year or so in a Union Pacific rail yard just north of downtown Salt Lake City. And it has nothing at all to do with the new coronavirus. A company spokeswoman for Union Pacific refused to answer detailed...