There's a FDR analysis, but I can find no mention of the CVR.
Several of the crew witness statements from the a/c on the taxiway comment that there was only one air traffic controller, working air traffic, ground and even vehicles. They observe that the single controller had a heavy workload, and was slow to respond to UAL's call of "He's on the taxiway".
For a major airport like SFO, isn't this a bit lightly staffed?