Just a note of caution on this. I travelled from Ibiza recently and, although you get priority boarding from departures (ie. CE group 1 called first), you're all hoarded onto the same bus. Despite being group 1, and first through, just ended up the first boarding the bus. Then almost last off it, too, as they ram them full with all passengers, which sort of defeats the object of 'priority boarding' to me.

Might be the same at Madrid.