I already worked in the department that I was hired as the Document Control Specialist for, however I was still required to interview. I actaully appreciated this since it was clear that equal opportunity was given to each applicant. I was not simply given the position.
On a negative note, I recall that those that interviewed me didn't seem to have a strong grasp on exactly what I would be doing. Now that I am in the position, I feel that including another Document Control Specialist would have been incredibly beneficial for both myself and the hiring supervisor to get a better grasp on my ability to perform in the position.