Back when I was applying, my MOC knew I had an LOA (USAFA) prior to me knowing. They had been notified electronically and I was notified by snail mail so when the notifications went out on Thursday, they were able to slide the information into my packets for both of my senator interviews that Saturday before my official notification came on Monday in the mail. I happened to have been at the Academy for a tour on that Friday before flying home to go to senator interviews so my admissions counselor dropped a hint, but couldn't say I had one outright. There was something special about a Medal of Honor recipient being the first one to officially say I had an LOA and questioned why we were even doing the interview because he knew I was getting a nomination. That was back in 2010, so I would imagine they do most notifications by portal now.
All of that to say, the academies are pretty good about official notification to MOC's considering they know what district you are applying from, but it never hurts to call and speak with the liason to make sure everything got into your package that you believe should be in there. Trust, but verify.