We have two customers: A and B. Customer A have users A.1, A.2, ... A.N. Customer B have users B.1, B.2, ... B.N. We need users A.1, A.2, ...A.N to be able to see and comment/modify all tickets opened by users B.1, B.2, ...B.N. On the other hand, users A.1, A2, ...A.N should be able to open tickets which are not visible to B users, but visible to other A users.