I really don't think Jo Calderone is run by Gaga at the moment at least.  If you take a look back at when he started to post:   You can see the tweets were aimed at Perez. It's true that Gaga did mention this Jo account in a tweet but I think it was more of a joke she had with Perez. Perez and Gaga were friends back then and this is why she perhaps revealed Jo to him prior to the VMAs and let him take a photo in order to tease little monsters.