In terms of the mechanics, and applying the ECB’s 33% issuer limit and subtracting the Eurosystem holdings of Greek government bonds, the maximum allowed purchases are € billion. Some could argue that the above amount is a mere pittance compared with the total Eurosystem’s purchases.
Even in this respect, the signaling effect of Greece’s inclusion in the 8/9  BIS central bankers' speeches  QE programme will be strong enough for GGB prices to recover, accompanied by a significant fall in volatility, as the overall financial environment is normalised and Greece is no longer an outlier in the euro area.