Wow, MetsPolice got mentioned in New York Magazine (in this article). Anyways..their take:
It’s safe to assume that if the Mets didn’t retire his number when his playing career ended — and especially if they didn’t do it when he went into the Hall of Fame — that they don’t consider him worthy based solely on his playing time in New York. But like we said, there’s no universal rule for such things, particularly under circumstances like these.
via Should the Mets Retire Gary Carter’s Number? — The Sports Section.