SHunter59:
What your husband is experiencing is unusual but does happen to the lucky few. In the 17 months following my CyberKnife treatment (CK is very similar to GK), I regained 15 dB of hearing in the 250 Hz band (which is the upper-bass frequency range) on my AN side. I did, however, lose roughly the same amount of hearing in my midrange frequencies. Dr. Chang thinks my improvement in the bass frequencies might be due to my tumor shrinking since treatment, thus removing some pressure on my hearing nerve. But it's anyone's guess why I've had this improvement, and whether it will continue or become worse again.
Your husband will probably not regain all of his hearing on his AN side, but any improvement is surely a great thing! Don't expect further improvement, but he might see a little more. It's unlikely, but hey, he's already beaten the odds!
Best wishes,
TW