I think in part it will depend on whether C is part of, or close to, the hierarchy in which A has authority over B. For example, if B is A's secretary, and C is a visiting client, it would probably be hard for C to interact with A and B as equals during the visit (and possibly after it as well). But if C is a tourist who meets A and B in a nearby bar after work, there would presumably be little difficulty in C interacting with them as equals, because their local power differential will be meaningless to C.