They are all reset.
This has become a problem for me, because I want to vote for @r0nd0n who has just become a witness, and whose character I believe to be unmatched, but my current proxy has just had a baby, and isn't paying much attention to Steem atm.
If I vote for @r0nd0n, I'll have to set 29 other witness votes because voting for one witness ends the proxy completely.