The NY Times published an article on the UP describing how various trade scenarious and tariffs affect its operations. The story describes different levels of impact such as what the railroad ships and where, to the materials for its rails and cars. Some prior impacts are mentioned as well. I found it very interesting; videos and photos are included.
Tomlinson Run Railroad
P.S. - Someone out there is drinking more than their share of the beer that the line transports :-). See the quote under the great close-up photo of the UP's flying flag.