So this thread is not left hanging, with the scepter of the coffin corner unanswered, ELAC in R&N
here said the following for the A330-200:
At FL350 and 210 tons my A330-200 (slightly different engines) would have had a barberpole at M.86 of 292 KIAS and a Vls 1.3G of 241 KIAS, a spread of 51 kts. A M.80 cruise would have been at 272 KIAS and the recommended TAPS would have been 260 KIAS. At either speed there would exist an approx. 20 KIAS margin to the nearest limiting speed, let alone the nearest actual buffet speed. That's a pretty wide margin to operate within and hardly anything like a coffin corner.
I don't have the same data for the 767-300.