There doesn't appear to be anything new about this recording, but thanks to this article on OpenCulture.com that I was tipped off by
The recording is from June 1st 1987 and was recorded at Grateful Dead's rehearsal spot - Club Front in San Rafael.
I've never been too hot on the Dylan and The Dead album and live recordings I've heard, but this is really great listening. It's a very relaxed rehearsal session with the band calling out songs, discussing the instrumentation, and finding their way haphazardly through a slice of the Dylan catalog.
The OpenCulture article has some interesting quotes from Dylan's autobiography about his surprise at these sessions because (in his words),
"the band wanted to rehearse more and different songs than I had been used to doing with Petty [on his recent tour with Tom Petty]. They wanted to run over all the songs, the ones they liked, the seldom seen ones."
Jerry is playing spritely and seems to be very confident on the Dylan repertoire. There's even some beautiful pedal steel in these recordings. Occasionally, the band starts really gelling, but this seems to be more of a discovery expedition to see which songs might feel good on the upcoming tour.
I've got to say, there's a lot of Dylan songs in this collection that I have not heard yet (and I'm a pretty big Dylan fan too).
I am Grateful to the twittersphere for tipping me off to this recording.