This is the world of business.
Exactly. Personally I would have a problem with this if no other options were available. It's quite clear that there are two other suitable hangers available to Ryanair to accomodate these jobs with the option of building this new hangar in the future. Unless Ryanair change their approach or Aer Lingus are bought out of their lease the story is over.
Ryanair themselves have published a copy of a
Hanger lease they have with the DAA themselves. It appears that even if the DAA wanted to break the lease the minimum notice period is 12 months along with providing relocation to a bulding of similar size.