Yesterday, the Daily News reported that the MTA had considered installing floodgates, in case a tunnel wall breaks. You know, somewhere there's a movie producer thinking "Let's do something that's The Taking of Pelham One Two Three meets Poseiden!" Amtrak has apparently upgraded old floodgates at Penn Station, and while the MTA won't get specific, the director of interagency preparedness Lewis Schiliro said, "To the extent that we can make the tunnels more secure, both structurally and from an evacuation standpoint, we've gone ahead and done that, or are in the process of doing that. We're not going to have a lack of imagination or a lack of concern cause additional risk to the riding public."
That's great because imagination eventually turns out to be part of maybe-terrorist plots. There are additional quotes confirming that the MTA's underwater tunnels are already pretty sturdy, and apparently the MTA has approved on $17 million to improve "subway tunnel defenses" - no robots, but there will be dirt and concrete as a barricade!