Hi!
"Most" of the MOC's in Arizona have, if they use the "Principal, Alternate" method, called the "principal candidate" once their board makes that decision. I was on Congressman Flake's (now Senator) board years ago when he used the "P/A" method and once we picked the principal, we called them and it was always the same day of the interview. The rest pretty much either email, followed by a letter, or simply with a letter.
But each year is different...they might have a new staff member, decided to change their method...you just never know.
Steve
USAFA ALO
USAFA '83