I just had a thought. Remember Nishi had a blog where he told the stories of the Tokyo team? Izumi mentioned there was a forum on that blog too. Perhaps Nishi had something hidden on that site for when the Catastrophe happened. Kei even made a point of mentioning that the word "Catastrophe" appeared in the blog frequently.
Nishi also mentioned other websites, where unauthrorised people like Kurono, Katou etc. don't have access to. Maybe he's trying to get into touch with other teams to exchange infromation on the aliens, business group and whatever else.