The OAA email is a courtesy to those who have been assessed so far - essentially, don't spend Christmas checking your inbox every hour to see if there's a note from BA Recruitment. It explains that some applicants have been rejected outright; some haven't met the criteria for progression on FPP but are invited to train with OAA outside the scheme; the remainder are still under consideration and can expect to hear something by the end of January.
Thankfully, I'm in the latter group and understand that I'm currently ranked highly enough to go through to BA HQ, but as other candidates are assessed and potentially ranked above me, I may find that I drop out of the cohort who are presented to BA.
OAA are being very transparent here and it is appreciated. I would be very surprised to hear of anybody getting a positive confirmation from OAA at this stage, given the contents of their email.