I seem to recall that MTH made a similar "passenger service" express boxcar that sort of looked like that, but not with that exact styling (it had the U.S. Postal Service logo on it). At any rate, the UP steam operation no longer has that specific car, as it was cornered and scrapped down in Texas about 4 years ago. Somebody didn't properly "tie it down", and it rolled out towards a live track, and got crashed by a passing freight train.
That stinks, as something similar happened to several of the former Freedom Train baggage cars in a UP yard in the 90s.
Was that the same boxcar used on most UP steam trips? I'd always wondered about that as I'd seen either it or ones like it on several of their trips over the years...
Last time I saw it was when 844 came up to WA state, as barely seen behind the 844's aux (former turbine) tender: