Does Union Pacific engineering have a specific need for one or more of the spans, or do they want to park them for stock? Bridge spans do get damaged, either from trains or from barges, so they could become good insurance for a quick recovery somewhere on the Western Rivers. Maybe, not even UP.

It is my recollection from long ago that steam era railroad bridges were designed with the presumption that counterbalancing of the reciprocating components of locomotives "wasn't perfect" (my term). Therefor, bridges were designed "very conservatively". (a long-established engineering term for "hell for stought"). Today, very elderly structures handle 286 loads.
Therefor, the Boonville spans may be quite valuable.

Comments from civils, mechanicals, and economists, please.