It doesn't seem to be working!!! I had few dozens ETH in my Mist Wallet before hard fork. I upgraded to 8.1 few hours after hard fork. I did two tests with spliting 1 ETH each time. 1 ETHs reached my other ETH address but nothing appeared in ETC address.
RE: Ethereum Fork: Step-by-Step Guide to Safely Splitting your ETH/ETC