Yes VOA is still on the air, but on a tight budget... That's the reason there are no public tours.. they simply don't have enough staff to cover it..
Some people thought this was the end of VOA..
http://www.witn.com/home/headlines/Radio-towers-being-demolished-in-Washington-373785161.html it's the end of site A (which as mentioned hasn't been on the air since 2006). Site B (Greenville) is still on the air..
There were originally 2 identical transmitter sites (A & B) and Site C was the receiver site) in the eastern North Carolina area. This is a pretty good overview/history..
https://en.wikipedia.org/wiki/International_Broadcasting_Bureau_Greenville_Transmitting_Station
One of the big challenges is they are still using transmitters manufactured in the early '50s (designed in the '40s), but they have a few, very talented and creative people keeping the aging hardware on the air. They remake some parts from scratch and stockpile parts whenever they find a supply of them somewhere in the world.
One maintenance aspect over time that kept Site B in far better condition than the Site A transmitter site, is that rather than frequently re-tuning given transmitters for the many different frequencies that they operate on, Site B set up specific transmitters on specific frequencies and did not re-tune unless absolutely required. There are considerable mechanical parts in the resonant circuits that have to be adjusted when changing to a different frequency.. That reduced the mechanical wear and tear on the transmitters at Site B.
There is no commercial market for the large scale power (250,000 & 500,000 watt) transmitters that they use, so newer replacement hardware is not available.
A friend of mine spent his career in the TV broadcast industry (tower construction/transmitter site side of the business), also a fellow ham, and he seems to know everybody.. He got in touch with Macon D. (he's in the news videos about Site A). That's how I got to go on the tour.
This is a good pictorial tour of the site
http://www.radioworld.com/article/48-years-old-and-still-a-flamethrower/23286