This information is available here; http://wiki.polycount.com/CategoryEnvironmentModeling?highlight=%28%5CbCategoryEnvironment%5Cb%29 You gotta look for it, but it's in a logical place
Theres a lot of custom brushes used, but nothing was accomplished by brush alone, its a great first pass to make with the lazymouse on so I can trail them over the major forms, but then each was hand sculpted with the clay brush and alpha 28 to make them work with all the other forms they interact with.
This piece is from the Outpost level, probably my favourite level in Gears2. If you note the subtle banding on the large open door edges, I did that with a clay brush and the square alpha 28 set to a very low 20 in strength. I did this to avoid exactly the problem TheWiruz was wondering about, having some sort of subtle…