Credit to Lord Funky Biscuit:
http://forums.whirlpool.net.au/forum-replies.cfm?t=1462202&p…
"While I think this is supposed to be restricted to the US, I just used a US address, paid with my AU cc, and successfully redeemed both codes on my AU XBL account."
More info from the link below - may be valid for any Summer of Arcade title:
"While the website states the deal is applicable with any Summer of Arcade title, the fine print at the bottom states that it only applies to Bastion. Tricky wording, to be sure, but it’s likely that the deal will be extended to future titles when they’re released. Upcoming games in the lineup include From Dust (July 27, 1200 Points), Insanely Twisted Shadow Planet (August 3, 1200 Points), Fruit Ninja Kinect (August 10, 800 Points), and Toy Soldiers: Cold War (August 17, 1200 Points)."
http://www.blisteredthumbs.net/2011/07/buy-a-summer-of-arcad…
That worked great, thanks for the tip. It even works out cheaper than buying the 1200 points, though the US address thing is a pain.