Nowhere.

Tracks all over the country have been tagged over the years with various names for the same operator (e.g. "CSX", "CSXT", "CSX Transportation"). I went through and made sure all tracks operated by the same company have the same operator value, and added operator:wikidata to mitigate this sort of data degradation in the future. The "longer variant" here is the name of the company without abbreviations, according to OSM conventions. 