This is my very cynical view, but at the end of the day given EU law and the fact that most Europeans will speak English, there isn't much that BA or Aer Lingus can do to stop EU nationals applying. I mean Aer Lingus could say you need to speak Irish, but that would only make 36% of their country eligible. Air France and I suspect Iberia put the language requirement in to prevent people not from Spain/France applying, but this keeps them within the rules of the EU. (Again my cynical view).