There are no public restroom facilities at D.C. area metro stations. The idea is to make really certain you won’t need them.
There are several things about this story that make little sense. First, there are rest rooms in each Metro station for the employees (hidden for the most part and certainly not for the public). Second, from the train area to them...it’s a one-minute walk but they aren’t supposed to get off the train until they reach the end of the line (typically a 75-minute run). They just didn’t want to walk the extra steps to get to it, so they did it in the tunnel itself. Delivery drivers, cops, firemen, and lumberjacks do it too....so it’s not really a big deal except some folks consider DC Metro tunnels to be sacred areas where you can’t do anything nasty (on top of the puke, the dead rats, and leaking sewage).
For some reason, on my list of 100 problems with the DC Metro system (I ride daily)...I’d rate this as 101 and not really worry about it. It’d be nice to have escalators that worked or safe trains or buses that ran on schedule....but if the chief achievement of 2011 was to stop urination in the DC tunnels...well...it’s not much to brag about.
Allegedly there are, but you have to use the secret code word "Emergency" to get the station workers to unlock them. I've never tested that myself.