THe old Paramount regime would have clearly paid the freight since that's what they did for S1 of "Happy Days" and the first three seasons of "Taxi."
But MGM has no legal claim to this and the other QM titles that CBS/Paramount is releasing because these were "Quinn Martin Productions IN ASSOCIATION with UA Television." That meant Martin retained the principal rights and thus whoever ended up with QM would have the last say, which turned out to be CBS/Paramount because Paramount took over Worldvision which had ended up with QM earlier.
In a similar vein, "Streets Of San Francisco" was produced "in association with Warner Brothers Television" which explains why CBS/Paramount has the rights to that, whereas "The FBI" was produced by Warners in association with Martin, and explains why Warners would have to release "The FBI" (and likewise why Martin's other show, "Twelve O'Clock High" would be Fox's call to release).