I personally do not expect Paul Simon to release any of his quad recordings in this day and age , same goes for his other surround albums. I think we all know this.Columbia controlled the masters back then, so he had no say in whether or not they got the quad treatment. But once he gained control, he moved his catalog to Warner Music, who were more cooperative with his wishes. He's since returned control to Sony Music, but that doesn't mean there will be surround SACD's. That was, supposedly, a stipulation of the deal.
Yes Columbia did control their artist master tapes , but so did the other labels . This includes Atlantic Records.
When they (artists) sign with the labels they $ell the rights to their music , usually for a certain time period , which can be renewed by both parties. Those rights for all stereo and quad releases become the decision of the respective labels. Rarely , back then .....,was there some give and take ,....such as Columbia wanting more quad from Wendy Carlos which she keiboshed (something of an exception). These deals always favoured the labels as is was the case in the 70's . Nowadays it might be somewhat more favourable for artists , those lessons have been learned from the past.
Another example is Frank Zappa who had to purchase ALL of his recordings back from Warner/Discreet (in the 70's) and at great cost but he eventually retained control of his music.