From reading threads at this site (and others) I believe there are 2 mounting holes behind the rear Scion emblem. You should probably search around to find out exactly where these holes are to make sure the xB badge would cover them. If you wanted to put the Scion badge in the corner where the xB was, you would have to shave the pins from the back of the emblem (or drill 2 holes). Of course you could buy a Scion badge somewhere that didn't have the pins.
Be sure to post picts!
Be sure to post picts!