Case T-154/10: Judgment of the General Court of (Sixth Chamber) of 20 September 2012 — France v Commission (State aid — Aid allegedly implemented by France in the form of an implied, unlimited guarantee in favour of La Poste as a result of its status as a publicly-owned establishment — Decision declaring the aid incompatible with the internal market — Action for annulment — Interest in bringing proceedings — Admissibility — Burden of proving the existence of State aid — Advantage)