This gets a mention in the notes to the cd issue of the Bill Evans album. Keepnews writes that Columbia failed to take up the option of the concert tape and it was subsequently snapped up by Fantasy. Presumably Columbia had lost interest in Evans by then.
I bought a number of Xanadu albums when they first came out. There wasn't much straight ahead stuff being relased and they looked very attractive at the time. I always felt that there was something missing from them and soon tired of them and I didn't keep any of them. I'm sure I'd feel much the same way now. The Gold series was another matter - some terrific stuff there.
I have the Avid set. I don't have the records to compare but the sound on the "Four Brothers" tracks is awful and a rather odd elsewhere. Treat with caution.
Despite having more less everything elsewhere I don't think I could part with "The Other Side Of Blue Note Box". It was a real treasure when it was released.