Well, my experience has been substantially the same as Nimrod's. Dredging through memory, early on in my punting career several WGs wanted to meet socially / off the clock, and I remember one of them promising BB as part of that.
Also there was one WG who used to talk through issues with her abusive boyfriend with me who offered it during a booking. But that's twice in 24 years and > 1,000 punts - and both those incidents were early on.
No definite offers in the last 20 years, though there have been one or two who laid back and opened their legs, as if to say "put it in". Never BBed a WG and do not intend to.
One thing I do wonder about, now OWO is more common, is how much safer BBBJ is than BB intercourse. They're both warm moist canals in the female body after all.