That really depends on what was on that compilation. There may be some sound recordings that have lapsed into the public domain. There may have been some that weren't, or are newer recordings of those older songs that are still protected. Certainly most of the compositions would likely still be protected by copyright, so there would have been some sort of back-end arrangement where the publishers likely were compensated to some degree for that, and to the extent that there were copyright-protected masters in there, there would have been some underlying deal. Of course, for the telethon, it was marked up substantially.
Unfortunately there are people who don't know about Spotify yet—