I didn't ask. But since they still do it I'd imagine they have some success with lessening the severity of the tinnitus. I read online average score before and after as 75 and 48, so a significant reduction in volume.
I think I am going to fly out there in a few weeks and have the procedure done. It's 3 days + 1 day for consultation. They said they'd schedule me starting on a Monday for consultation since I'm from out of town, so I can have the procedure done Tuesday, Wednesday and Thursday. There is a hotel just up the street I can stay at.