From the agreement between Aer Lingus and the DAA regarding Hangar 6:
"save that it is expressly acknowledged that notwithstanding anything contained in or implied by this agreement if the licensor requires at any time the licenced area or any part of the licenced area for the purpose of the aircraft operation or development of Dublin Airport the licensee shall yield to the licensor the full free and vacant possession of the licenced area."
In this case, the Licenced area is Hangar 6, the licensee is Aer Lingus, and the Licensor is the DAA.
No wonder Ryanair want to buy the Hangar rather then lease the space from the DAA under these conditions. The DAA have been doing this for years and not just to ryanair: car rental companies, self service check in kiosks and baggage handlers accommodation have all been "moved to facilitate the development of the airport" by the "licensor" in the past, and in all cases the "new licenced areas" have been provided at a hefty increase in the rental costs.
So essentially, a "lease agreement" with the DAA under the aforementioned terms is merely the equivalent of selling your soul to the devil.
PS: The aforementioned terms also indicate how the DAA could exercise this clause in it's agreement with Aer Lingus in order to facilitate the sale of Hangar 6 to Ryanair: this would definitely facilitate the "development of the airport," would it not?