They're not real iirc... the OT is NYC and ID is 01234, is that the one you're talking about? All of the Pokemon the NY Pokecenter ever offered had their OTs based on the machine they were downloaded from (PCNYa or something, IE machine A, machine B, etc), and the ID corresponded to that as well. Mew was never given away there, the only English even Mew were the MYSTRY ones. Many people do offer them, but I don't think most realize they're fake.