The TV stations have had unions since the 70’s/early 80’s. Especially in the news departments. KGW and KOIN had additional operators/engineers unions, too, at least historically speaking. Nowadays, I don’t know since most workers have been fired and replaced with a computer.
Actually, all of KING Broadcasting had unions, including the radio units. Most Seattle radio stations were still under union contract until atleast the mid to late 80’s.
I may have shared this before, but when I worked at KIXI-FM in Seattle in the early 80’s, we had a nice minimum salary, (which is likely still being paid in the same dollars, or even less today, but I digress), and we also got paid for any spot we recorded that aired on a shift outside of our own. This was the big-city way of doing it, but it did not last. Atleast Seattle, to my knowledge, never had union rules regarding running your own board, because that skill would of course go on to become a much needed requirement in the late 80’s and and beyond. Chicago and NY would not allow the “talent” to run their own board, unless they voluntarily declined that union prevision.