Here's an essay on the structural aspects of the film, touching on the screenplay and novella as well. You have to register to read it, but it is free.
Edgecombe, R. (2007). The Formal Design of "Brokeback Mountain". Film Criticism, 31(3), 2-14. Retrieved from
http://www.jstor.org/stable/24777357At first, the florid writing put me off, but there are many interesting points that make reading it worthwhile.
