My last flight was the day before my BAEC end of year, but the details posted on my account after the end of year and tier points had already been reduced to zero for the year. There was also a 'Balance Adjustment' the same day as a seperate item which presumably would have canceled out anything I had earned.

Being aware of the dates I had booked the flight on Avios so did not have any points to lose, but I think the 'Balance Adjustment' would have zeroed out anything earned before the end of year but posted afterwards.