The National Guard is patrolling the NYC Subway system? Since when? (Not doubting, just want clarification and information).
Armed National Guardsmen and women have had a pretty steady presence in Grand Central Terminal and Penn Station, and maybe the Port Authority bus terminal too, since September 2001.
They don't patrol the actual subways and subway stations, best I know.
There was also a couple of armed National Guardsman at the Metro North White Plains train station yesterday, but I had never seen that before. To be fair, I am very rarely at that station (2x a year or so).
Just since the second (fizzled) attack on the London tube last week, I believe.