I tried figuring it out, but I couldn't get the sleep switch pinout (Apple goes to a lot of trouble to obscure the traces with the silkscreen and both my multimeters are wonky—they don't like displaying correct values). Now it's in the DIY-intosh and it still doesn't default to outputting to the external screen. I can only hope that it doesn't work for the same reason that Firewire Target Disk Mode doesn't work; OS X hasn't been installed yet.
As always, click on the pictures to see the hi-res versions.