Well the original announcement was only Europe (because America had the real-life events), then it was announced to be in America and Australia too. Now it's also on the South American part of the official HG/SS web site, so it's available in many places!
This implies that it may be available in all sorts of places, so give it a try! You just go to Mystery Gift in the startup menu, then receive via Nintendo WFC. You need a wireless internet connection.