I also think the idea of using the Spanish FAs as strike-breakers wouldn't work, because the baggage handlers etc. would most probably stage enough wildcat strikes to severely disrupt AY's operations in the case of a FA strike.
I view this is as flexing muscles by the AY towards the unions in preparation for the wage negotiations. "Look how much we are willing pay to have these people in reserve. Getting labour costs down (per km etc.) is important for us."