I know that moderator can manually refund a bounty, maybe even old one.
However I could not find any documentation explaining what happens when a question that had bounties set on it is being deleted.
I'm not talking about active bounty set on the question in the time it's deleted, but rather old bounties that were set, expired and granted in the past on that question.
From my own recent experience (deleted question on http://movies.stackexchange.com), the bounties I had set there have been refunded but I can't see if manually by a moderator prior to deletion, or if it's automatic process.
Update: Deleted just now old question I had here on Meta with old bounty as well and I got full refund. So this is automatic process. Would still be nice to get official response explaining if this was always the case, or if it's some new behavior.