I was just reviewing a 747-8 AFM revision (something I need to do with some regularity), this is what it says:
"The maximum operating limit speed shall not be deliberately exceeded in any regime of flight."
I think the key word here is "deliberately".
BTW, 747 MMO is 0.90 Mach. During the 747-8 certification, I looked at a whole lot of data that was 0.97 Mach and higher (flutter testing and the such), and the airplane didn't break
