For starters, there is no shortage of examples on PSN of PSOne titles from publishers that are defunct, have been dissolved after acquisition by a larger firm, or companies that have merged to form a new firm (Such as Square Co. and Square EA, both of which technically don't exist now).
Secondly, I'm privileged to know some of the inner workings of this process when the two Oddworld titles were recently released on PSN.
May I ask where your statement originates from?
This list is for PSOne rereleases on PSN. There was never a Call of Duty title on the PSOne, and the original Call of Duty has never had a console release until now on XBLA and PSN. You'll find it with the other original releases on PSN, not in the PSOne section.