The PFE was founded in 1906 and jointly operated by both UP and SP starting in 1907 and lasted until 1978, when they ended their alliance, and the resultant inventory of refrigerator cars was split up between the two; although now it's wholly owned by UP. Western Pacific joined the operation in the early 1920s and stayed with them until the late 1960s when they decided to go with Fruit Growers Express (FGE) instead. No other railroad was ever part of PFE to the best of my knowledge.
So in the early 80s you would have still seen a large amount of PFE cars still sporting the joint SP and UP logos together and would continue to see them this way while the post-split paint schemes with just one road or the other's logo with SPFE (Southern Pacific Fruit Express) or UPFE (Union Pacific Fruit Express) reporting marks would start to become more commonplace over time. The roads often times didn't bother doing a full repaint and leave the legacy cars as they were until they were retired or as part of undertaking damage repairs or rebuilds.
