SSully, I will do my best to answer your questions (with what I THINK to be true at the moment).
1) No, I don't think there were ever any discrete 4 channel reels sent out to radio stations. I have transferred a bunch of shows and have never come across one. Plus, the logistics of dealing with 4 track reels would have been way to complicated and expensive for stations to deal with. By comparison, an SQ reel is plug and play, and it would be up to the listener to get the right gear to make it all work.
2) Remixing of quad mixes - I haven't heard every last one of the commercial cd releases of the shows, but all the ones I've heard are remixed. ELP was definitely remixed. This is a very confusing show as far as mixes go.
I was probably unnecessarily complicating the question, by using as an example something that was broadcast in matrixed quad.
A better example would be a KBFH show that was mixed and broadcast in stereo only in the 1970s/early 80s, captured on a bootleg, and later (after the '82 fire) released on CD officially. Does the CD release sound remixed (not just differently mastered) compared to what was broadcast?
There are actually 2 different quad mixes. One was for the album release (which got folded down to stereo). Then the quad mix for King Biscuit is actually a little more straight forward than the album mix with less efx and panning stuff going on. The stereo mix for the cd does sound very similar to the original broadcast mix in stereo.
And that would be the best comparison, not a comparison of quad to stereo.
3) rebroadcast of quad mixes- Yes, I have found encoded mixes on broadcast cd's. While there was a fire and tapes were lost in the early 80's, it seems like there must have been some production masters that survived.
4) Brickwall limiting on Yes show - Later King Biscuit broadcast cd's have progressively more and more limiting on them. The early ones much less so.
I guess that was the underlying question. Was KBFH ever 'baking in' compression to its products, or was it added by radio stations?
Hardcore digital compression didn't become a thing until the late 1980s, so I would be surprised to find it on any for-broadcast CDs made before then.
Another issue I have found is that the first two songs of the show (Sound Chaser and Close to the Edge) were printed to tape extremely hot (way too much so with lots of distortion) and the wave forms are all clipped even before the limitting. I think the existing version of the show we've been hearing for years MIGHT be a production/duping master which was less than perfect. If any other reels show up from the early broadcasts of this show it might be worth comparing. I have a version of sound chaser from a 74 "best of" show which sounds noticeably cleaner from what I remember, which makes me think the (lost) master might have been what they used for this cut.
I have at least three different-sounding surround 'decodes' of this. One is OD's from 2012, another is from 2019 by a 'guy' who 'developed his own process with guidance from OD' (and this one sounds the best) , a third is by someone else entirely. All show to be compressed in dynamic range and limited in frequency range. This could be due to the 'mastering' choices of the persons who did the decoding, or it could just be baked into their sources, I just don't know.
The Wolfgangs vault version is encoded, with the exception of Ritual, which is just stereo. Having said that, the encoding is very messed up and will not decode "as is".
Was it ever losslessly available from Wolfgangs? AFAIK, WV downloads these days are mp3-only. This is what I was told, I haven't done any
FWIW I can say that when I use Audacity to record the streaming audio of 'Close to the Edge' that's available on the site, I see no evidence of clipping, nor obvious sign of lossy encoding. The recorded wav file displays no shelving in a frequency scan, nor does the spectrum show any abrupt shelving or hard low pass filtering, as one would expect from all but the best quality mp3s. So this is a high quality mp3 if it is one) . There is audible content to at least 17kHz. The audio sounds 'hot' ; Eddy Offord , who oversaw their live sound back then, liked pushing things into the red. But that's old school distortion
None of which is as dispositive as having a confirmed digital dub of 'master reels' audio to compare it to.