The source code to Apple's branch of gcc is open and available, includes everything except the mods to libobjc. The denizens of Apple's objc language list have figured out some of the features (not perfectly). The syntax should be decodable from the compiler as well, but no one's posted any of it. I agree that most of the syntax is highly lovable.

Allan will probably eventually incorporate the feasible Xcode 3 enhancements into TextMate via extensible architecture.