Although I'm speaking from the Boeing aspect, I'm sure brand A does something similar.
There is a specific option package for operating out of airports above 8,000 ft. Among other things, it allows setting the airport altitude above 8k (up to, IIRC, 15k) and prevents the cabin O2 masks from dropping up to something above the selected airport altitude. As gf noted, the flight crew should be on supplemental oxygen whenever cabin altitude is above 10k.
A few years ago we were looking at a high altitude option for the 747-8F in response to operator interest, but ultimately nothing became of it.