The surveys I have seen have been very general in nature, covering things like lenght of sobriety, age groups and gender mix, giving an overview of current membership, never anything about recovery rates. The one survey that I saw taken was back in the eighties but only members with more than five years sobriety were invited to participate if memory serves me correctly. Anyhow, I hadn't been sober long enough. I remember thinking at the time that it was a very conservative approach.
A survey of recovery rates would, I guess, have to run over a good period of time with extended participation of members. I have never seen or heard of anything like that.