>>1432740Considering the JUST-ed state of railroading in America in the 70s and 80s, if a steam locomotive was still operating on a Class I railroad at this time, it would likely receive no special treatment at best- at worst, it would be in far poorer condition than in its heyday.
I envision a very tired-looking locomotive- paint fading, detailing and metalwork rusting- chugging along laboriously as it hauls a string of dingy, mismatched high-roof Pullmans and streamlined coaches through the industrial wastes of the Northeast Corridor. A best-case scenario might mirror what they actually did to the 4449 for the Freedom Train: if Amtrak, for instance, took over the operations, I see a refurbished but garishly-painted locomotive and consist- with tacky, retrofitted Pullman cars.
As for you hypothetical, there was a situation similar to what you proposed with Pennsylvania #4487: it was GG1 built in 1939 and ran under both PRR and Penn Central colors. In the 80s, it was refurbished to original PRR colors and nicknamed "Big Red-" used for a farewell season on the NJT between 1981 and its retirement in 1983. Even today, some locomotives in the US, though modern, will be repainted in heritage liveries- which is the closest we'll probably get.