Thanks to Alex Ross for posting a link to the Schoenberg spricht archive of the Arnold Schoenberg Center. The texts from all of the recordings--even the long ones--are clearly transcribed. Someone put a lot of work into this, and I intend to put a lot of time into reading the transcriptions.
By the way, the date that Alex Ross calculated as the 100th anniversary of atonality, December 17, 2007, is also the 237th anniversary of Beethoven's baptism, though his birthday is celebrated on December 16th. I guess, like the actual birth of atonality, we really don't know exactly when Beethoven was born. But it is interesting to have some kind of measuring device, like a dated manuscript (which could have been written on the 16th, or even earlier, but was dated on the 17th).