Recently I had cause to cancel an Avios ticket using the ba.com web site. Whilst the taxes re-credited immediately the Avios were outstanding 3 weeks later.
In the interim I had called and been told that it took a little while for the Avios to reappear.

Today, it seems I spoke to someone who knew what was really happening. It appears that the recent BA upgrade has caused some cancelled award tickets not to go to the correct queue for crediting. Having explained this, the helpful agent stuck the ticket in the right queue and voila – a Redeposit showing in my account!

So, if you’ve cancelled a ticket recently check you got miles as well as the taxes back!