If you are a class III SOT, then if you have a leo/military demo letter then you could get one. (There's one on sturmgwehr right now).
Keep in mind that most people who own class III (title II) firearms are not class III SOT's, but just people who fill out the forms, get the law enforcement signoff, and send the paperwork to the atf. So unless you want to deal in class 3 weaponry, then no, you will probably not be able to get a glock 18 (although there are rumors of fully transferable g-18's out there.
Or that's my understanding of the law.