Hey Ben,
I replied to your post about this in the uva forums. Again, a great find!
I wondered if your friend told you the exact source. It's a very good find and I listen to it like 5 times a day. It doesn't seem to be recorded from a scanner... as everything is revolving around one flight, UAL975. Everytime 975 is handed a freq change, usually the next thing you hear is 975 checkin in with another controller. I wonder if it's recorded from the flightdeck or perhaps the from the ATC channel that UAL provides as part of the inflight entertainment.
Rob