Quote from ReNoI haven't done any of it myself, but I'm sure its still heavily brush based in order to flesh out the shape of the level. Like Unreal, it uses a lot of meshes for detail purposes, but you still build the basic level out of brushes in Radiant or whatever.
Yeah that's pretty much correct. You build the main hull of the level out of brushes, and then use statics when you want to add some detail.