It is also, as far as I know, illegal to hack or disrupt computer networks in that way (even for the NSA). If they had warrants giving them access to information they wanted it would have been overkill to do something like that, risk getting caught, and now have to go to the company for intelligence cooperation in the information.
and if the NSA should break the law that makes it illegal to hack networks in this way, what would be its punishment? Do we send the NSA to jail? Do we fine the NSA? Who do you think pays the for the lawsuit (punishment, legal team, etc) when the NSA breaks the law?