I read about this when I was doing local comps back in the mid 90s. Never made much difference, other than finding out bucarb is an effective laxative. Don't say i didn't warn you.
It has been suggested that the more highly trained athletes are less likely to benefit from it because their body's natural buffering systems are already so well developed, but so far, this is just speculation.
Bit of a digression, but is developing lactic tolerance specific from limb to limb, or would doing more aerobic exercise improve my general lactic tolerance or just that of my legs. I.e. will, say, cycling get my arms lactic tolerant, even though they don't get a work out? If so, my thinkin is that my sesssions could get extended by doing more aerobics on days off bouldering, along with the cardio...as you can tell, i ain't no sport science person.