From what I understand from other Green Day fansites, none of them have a Twitter account. There is an official Green Day Twitter page, I don't think the individual members have personal Twitter accounts.

Thats Defiantly mikes.Not so sure about billie.If you look at Billie joes comments it dosen't look like its him.And if you search billie joe armstrong it comes up with like 10 billie joes.

seems to me completely fake. but is just an opinion.

Yeah, Billie has one, I'm not sure what it is, but I saw one of his Tweets in Kerrang, it's about them staying at the same hotel as the Jonas Brothers and he's the 4th Jonas called "Billie Jonas" lol bless him, there's already a fourth Jonas