Just stumbled across this thread and had a couple of things to add, and I apologize for any redundant info. Also, am enclosing a couple of questions regarding some quad shows I need some help with, so hope you don't mind.
5) WXRT Chicago apparently made a bunch of SQ broadcasts in the late 70's. The most famous of these is the Genesis Uptown theater show from 1978, and also a show by the Cars. Been trying to find any kind of listings, and there is virtually no info to be found out on the web. Heard that the tapes might actually be getting digitized, but rebroadcasts are incredibly rare if not nonexistent because of the usual licensing issues.
6) Elton John 2 part SQ King Biscuit May and June of 75. If anyone knows any info about this one, would love to hear it. Haven't been able to find any tracks or info from this show. Also, Elton didn't do shows in 75 until after these broadcasts were made, which makes the broadcasts even more of a question mark.
7) Was told not too long ago that the BSO quad broadcasts that used two radio stations had one station carry the left channels and the other station carry the right channels, as they couldn't agree on who would get the fronts and the backs.