If that's the extent of officials' concerns, it seems like there's not much to them. (For the record, they haven't commented beyond admitting the potential legal action.) The level's creators rightly point out how they made the metro stop in the first place: by going down there and looking around. No one is being stopped from doing that, and the game doesn't reveal some secret important information that could be detrimental to the public. If the transit authorities think it does, they're just demonstrating that they don't understand what goes into making a level like this: simple observation.