Taken straight from the Joystiq news piece-
Gears of War has been pirated and uploaded to an Xbox 360 binaries group on Usenet. The file clocks in at around 7.2 gigs in 157 parts, and will require someone with patience, bandwidth and no sense of morals to download.
Is it real? Nobody knows. While it is hard to imagine this being legit, it definitely represents a problem to the developers.