No, file notifications are not yet supported on Mac OS X, as detailed in the other answer.
I'd guess that one reason for that is that on earlier OS X versions, notifications were limited to telling you that something had changed in a certain directory; it wouldn't tell you what in that directory had changed. Given that limitation, the API on the Emacs Lisp level would be rather inconsistent.
File-level notifications were introduced in 10.7 (Lion). This questionThis question contains more details. As I understand it, it should now be possible to implement this functionality for Emacs on OS X.