The AMA mods often arrange high profile AMAs amongst themselves -- or with the reddit community staff involved -- so it's likely they were aware before hand. I

The AMA mods often arrange high profile AMAs amongst themselves -- or with the reddit community staff involved -- so it's likely they were aware before hand. I can't check the sidebar because reddit isn't responding, but they normally have the "upcoming" AMAs in the sidebar and lots of are listed days/weeks in advance.