You can't copyright a title. I could write a book or movie called "Brokeback Mountain," for instance.
Now, the *story* of the current "Brokeback Mountain* is copyrighted, so my version could NOT be about gay shepards in Montana. I'd have to come up with new characters, a new plot, etc. My "Brokeback Mountain," for instance, would be the story of a U.S. Infantry Squad fighting it's way through the Italian Mountains in World War II.
The problem is, if I released that movie now, most of you would get it confused with that *other* "Brokeback Mountain* and would skip my movie. That's why you'd want to avoid distinctive titles that have already been used. Still, titles can't be copyrighted, so I could name it that if I wanted.