The Pennsylvania seems to have stopped accepting them following a February 3, 1955 derailment. There is some New Haven archival documentation as a source for that, found here:
https://www.rypn.org/forums/viewtopic.php?f=1&t=22665This ban by the Pennsylvania seems to have been enough to get the New Haven to convert the rest of their cars, but its not an AAR ban. There was a proposed ban, but it didn't get the necessary votes. Even with a ban, you can keep running things on your own railroad, which for head end equipment means it could stay in service for quite a long time as is.
