I doubt it's SQ encoded - 3 or 4 tracks from this concert were broadcast as part of the 'Supergroups In Concert' radio series, but the full show didn't surface until about 10 or 12 years ago. Supposedly the whole show was going to be released officially, and then negotiations broke down or something and someone at KBFH leaked a DAT of the show in to trading circles. Subsequent to that a few of the tracks from this show ended up on the official live compilation 'Past Lives'.
It's my understanding that a fire destroyed all of the KBFH masters (ie stereo and quad mixdowns) some years ago, but it was later discovered that all the multitracks were stored elsewhere. That's why all the KBFH stuff that's been released digitally, both on CD and for download at places like Wolfgang's Vault isn't SQ encoded - it's not because they hated quad or anything like that, it's because the masters are gone so they were forced to do new mixes from the surviving multitracks.
I'm not sure if the original 20 minute 'Supergroups' radio broadcast was SQ encoded, although even if it was I'm not sure how much quad you could get out of a guitar/bass/drums/vocalist live gig anyway. Having said that, it's probably the best live audio document of Ozzy-era Sabbath ever captured, and a shame it's never been released in it's unedited form.