The FT’s Alphaville blog has a re-cap of the ECB/BuBa drama and great comments from a Nomura strategist who says that the ECB will only target short-dated bonds (< 1 year) and only a country makes a request for EFSF aid.
He says the ECB will guide expectations rather than setting a cap:
We believe that identical and unconditional yield targets across member countries are currently impossible to fathom. In fact, it is likely illegal under the treaty.