Kfuddle
A320 VMO350KTS, MMO M.82, VD381KTS and MD.89.
Only A380 has MD M.96
According Airbus
1. critical loss of lift due high Mach is well beyond the normal envelope and MD.
2. In level flight at high altitude, drag increase prevents MD from being reached. In flight tests MD is reached through specific manoeuvres (dives with full thrust are necessary)