The UBS hold was mostly about providing liquidity to the shorts...

The UBS hold was mostly about providing liquidity to the shorts (and driving down the price to make $$)- the fact they are buying back and selling down will coincide with their customer buying back borrowed shares which they have created the liquidity for them to do so... for a small fee of course!
They also traded short off their own book, no doubt.... anyone who has had the pleasure of holding a stock which UBS has taken this strategy will feel my pain... who says stock prices can't be manipulated - all you need is a lot of capital!!!

Take a look at:
http://www.shortman.com.au/stock?q=acr
for the short holding trend here.