Just a guess....but it probably does have to do with keeping the road name active. It is likely that Spokane International still exists as a corporation, although all stock is owned by UP. Probably the right-of-way and MOW equipment is in the name of Spokane International for tax and real estate purposes, and possibly to avoid having to re-write binding contracts that were originally made with an independent SI and which UP inherited. Union Pacific controls a lot of these "paper railroads", at least they did until fairly recently - I'm not sure what recent changes have been made at the corporate level. Even the ancient "Oregon Short Line RR Co." shows up occasionally on legal documents. This happened recently when a branch line near my home was abandoned - documents pertaining to the reversion of ROW to adjacent property owners all referenced OSL, as the original agreements for right-of-way had been with that company.