I guessthe routes taken by UP trains east of Omaha do not host any Amtrak trains, since Amtrak does CHI - Omaha on BNSF?
If fact, the route taken by the "Cities" streamliners is entirely freight only from Alazon, NV (near Wells) on east. East of Omaha, the former C&NW is freight only until the Chicago commuter district, and the Milwaukee Road, used by the Cities after 1955, has been torn up.
The UP route from Cheyenne (Speer) to Denver used by the City of St. Louis is freight-only, and the cutoff from Julesburg to Denver used by the City of Denver is partly abandoned, and the rest freight only, and the KP from Denver to Kansas City is freight only. I am not sure whether the former Wabash from KC to St. Louis used by the City of St. Louis is still there and freight only or abandoned.