Eurex could further increase its stake in European Energy Exchange (EEX) beyond the 45% stake which it is looking to acquire, but political walls could prevent outright ownership.Eurex signed an agreement to acquire another 20.85% stake in the Leipzig-based exchange for €55.15m, thereby increasing its shareholding by up to 44.07% from the current 23.22%.While Eurex gave no indication that it would further increase its stake one market source said that Eurex...