SWH, I'll try to help the Boeing fan boys out
One airline "with which I am familiar" is currently running the A330 at CI49, and the A340 at CI54, both equating to around M0.82. For reference, LRC on the A330 is approx. CI40, or CI50 on the A340.
Therefore, given a
real world airline is currently flying its Airbuses at a speed approximating LRC, I would expect it will run its A350s close to LRC also which, as previously mentioned, equates to M0.85.