O yes, John Cale has been taped without his permission. Some very naughty people put this on shingu circular discs and larges pieces of vinyl and put them up for sale for ridiculous prices. However, there are a couple of bootlegs from radio broadcasts which sound really good. And there is a plethora of fan recordings out there. Some of these sound great, some sound awful (the "completists only" tag is an often used euphemism).
Does John Cale approve of unofficial live recordings? No. On the other hand, people collecting and trading recordings own most of his released stuff.
Just ask, and be polite. Very polite. And be patient. Any fan collection will grow, slowly at first. Learn about B&P, FLAC, SHN. Use terms like: WO, WC, ISO and become a hardcore Caleist. And never, and I mean never, beg or whine on the John Cale mailing list.
Most of the recordings in this section capture a live performance, others contain unreleased and/or hard to find rare tracks. There are 402 recordings in this section, and my guess is that this is just the tip of the iceberg (well, I actually know it is, this section is updated nearly every week, so ... I can't seem to get rid of the backlog of recently surfaced recordings demanding my attention).
Recommended further reading:
John Cale Gigography
Maintained by Cyrus. A list of all known live recordings.
If you have live and rare John Cale recordings and are willing to trade, drop me a line. I don't buy, I don't sell. Don't bother asking me.