Our first clue was that the pre-release version of Tom Clancy's Splinter Cell: Double Agent, which installs to the Xbox 360 debug hard drive, contained an option for 1080p support. The option was buried under the system options in the console Dashboard -- easily overlooked.
Once we noticed the new option, we immediately followed up with Ubisoft. Would the retail version of Splinter Cell: Double Agent also support 1080p output on the retail Xbox 360?
A Ubisoft representative's answer was short and to the point: "Yes."