I remember the Caps used to do that to us in the playoffs all the time. They'd block ticket sales to people in the 412 area code. Building was still full of Pens fans every game.
I don't think the NHL mandates an allotment for away tickets (ie; the way college football does), or that the Wings would do such a thing. If they do, then kudos to them for welcoming Pens fans warmly.