We found quite useful to allow specific users (normally, also requestors) to access other requesters' requests. This should be user based and not dependent on department or site. As example, I do not want my department or site colleagues to have access to my HR confidential requests, where I discuss about my pay slip and career management. I want to decide in which requests I want specific users (likely, also requesters) to access, being able to see all progress and status.