IAG have responded:
Legally binding agreement will state slots, cannont be sold, tranferes and all current LHR routes kept for 5 years. Not sure if it all covers 5 years or for example they could drop any LHR route but the slots will still be used by EI to increase elsewhere. Dublin HQ also kept.
Aer Lingus shares closed up 3.5 while IAG dropped 2.7