http://www.autohebdo.fr/endurance/le...le-calendrier- has a short interview with Ullrich.
He claims that Peugeot was better on the ILMC tracks because they started developing/testing much earlier than Audi. While Audi was working on their Le Mans setup, Peugeot had already done their Le Mans preparation and could adopt their car for the sprint ILMC races.
He also explains that they will only run with hybrid system if they are convinced that it has a performance advantage and if the system is completely reliable.