This recording was originally released in 1967, but according to Wikipedia, it was only later "... In the early 1970s, [that] Vox and its subsidiaries issued a number of compatible quadraphonic/stereophonic recordings." Also, as per the original liner notes, "... The four special ribbon microphones, designed by Charles P. Fisher of Cambridge, Massachusetts, were so disposed as to preserve the integrity of the STEREOPHONIC relationship..."
While it's conceivable that Quad versions, if there were any, might have been extracted from the 4 microphone feeds, there's no indication anywhere that they were recorded on separate tracks. OTOH, this SACD has a photo of the original master tape used for the transfer, and finally, even the 1999 DVD-A version is apparently stereo only.
Regardless, this is a very vivid, wide and precise - albeit a bit dryish - stereo recording, masterfully preserved in pristine DSD sound by the Analogue Productions team.