Interesting counterpoint: by federal law, interstate railways have the authority to appoint their own police; they are the only private entities in the United States that have such authority, and state and local governments are not allowed to block or interfere with it. So if the Union Pacific is having issues with theft and/or vandalism around the trains, they already have the authority to deal with it themselves on a level that is unheard of for any other business.
(Railway police are the sole case where a private company is authorized to have its own police. Other private companies can have security officers without police authority, or they can hire actual police officers, but the authority of those police officers still flows from the city/county/state. Railway police answer solely to the company while still having full police powers.)