Since 1975 is more than 17 years removed from 1954 how many of those patents were still in force in 1975?
The last order of Hi-Levels by Santa Fe was 1964. Perhaps there were some new patents?
Bombardier built the Superliner 2s and had use of the plans of Pullman-Standard. Don't know how they acquired the rights. Plans are still intellectual property even if patents are not involved. Pullman-Standard went out of business and the Superliners were the last cars they built (they were primarily a freight car builder by that time). Budd is long out of business as well.
I don't have the answer to that one...I can't recall where I read that Pullman bought certain Budd designs to build the Superliner's....perhaps they bought some "trade secrets" that don't expire? Not sure...