Quite a few years ago I was working a week of NRT-PEK-NRT night flights. I think we did four of them. I can't remember the exact trip number but it was something like 86P. Every night we worked the inbound back to NRT 86R would also show up on one of the freqs that Tokyo was using. And one night we had 86P, 86R and 86S all on the same freq at the same time. One crew (not us, thank God) had a tough time figuring out who the controllers were talking to. The captain I was working with wrote a safety report on it. It was obviously a very effective safety report.