I'm having an hard time answering this one, because as far as I remember Malpensa's layout (of both terminals) I don't see a way an automatic boarding gate can help you.
In Malpensa (well...as far as I can remember, in all the European airports I've been) the first barrier you hit is security control, and you can pass it only with a valid boarding pass: good luck squeezing behind your friend so that the guards will not notice you :-D
Editing in more details because I'm not sure I've understood the question enough to have given a proper answer.
Malpensa T1 departure's main area, the first you walk in from outside, is a huge hall in front of the runways, where you can wander freely, take a coffe, buy a ticket, watch planes, go upstair for an hamburger at
McDowell McDonald's, use toilette, check-in, and so on.
Next, to go somewhere else, you have to queue at security: if you can sneak past them...you are a ninja.
Side note: T2 departures is exactly the same, apart from being a small and dark hall where the only thing you can do is to queue for security.