but even if you can search throughtout all tickets, you doesn't have access to tickets belonging to depts you don't have access to. What is the rationale behind "search for tickets you will not be able to view" ? if you don't have access to a dept, you can select this dept for a search, but as it is coded today, this will return no ticket at all (except for tickets you are assigned, but I'm not sure why a ticket belonging to a dept could be assigned to a staff that doesn't have access to that dept. dept transfer is better in this case).
so because your result list will be empty, why showing this dept ?
think of a large enterprise dealing with a lot of products and having a dept for each product. if a staff is only allowed to access dept "product_A" and dept "product_B", why offering him to search tickets regarding product_C he doesn't have access to ?