I'm fully aware that the M5 is MHV route, because I live in Manhattan. And MHV9218 I caught 4429 when it was just traded to MHV here video proof: NYCT: Orion VII NG #4429 on the M2 - YouTube
It was traded back to MJQ from MHV and it was on the M5. Why? I really do not know. I saw it during my lunch break at 73rd street and Broadway. It had MHV stickers when it arrived. It is now in back at MJQ.