I can try DerKaiser but you probably won't like it! As far as I am aware, these are Lower Tier II securities. These securities are only slightly subordinated to senior debt. They typically don't usually have loss absorption features written into the docs. Therefore non-payment of interest or principal write down is an event of default. That is why the offer is voluntary. A 70% haircut on these securities is seen as quiet penal but I accept that there is a valid argument for 100% haircuts considering the state we are in.
I should add that they are currently looking at changing this after 2013. (Not much good now I know!)