FWIW, the terminal BA uses [Concourse A] is right next to AS's terminal and you do not even need to go outside to get to the AS terminal... SFO is ^ in all areas, except when the fog hits, however, all of BA's flights depart in the evening, and that is when the fog issue is generally not an issue... Most of the time the fog hits in the morning or late evening...

Remember, TATL flights has priority and even if they depart 2 hours late, they always manage to arrive at the destination on time or with minimal delay