People's perspective often decides whether or not teamwork is achieved.  Sometimes barriers are created just by organizational structure yet there are no real obstacles in the way.  We periodically adopt an "us" and "them" attitude with no concrete basis of conflict.  There are ways to perform within the boundaries of set policies and still reach out to those functions that live in someone else's realm.  A great deal of those motivation books that make people rich are full of mythical ideology that just leaves you thinking that you wasted your money buying the book and could have come up with the solution presented on your own.  I've found the only thing that helps is an honest assessment of the problem, a workable plan between components, and trust.  Are you a team player?