Not an Original PBS Program?
I believe that this was originally broadcast on the UK version of National Geographic channel:
http://natgeotv.com/uk/nazi-megastructures/about
Or perhaps portions of it. I'm sure I've seen this before, but not on PBS.
They do this all the time. Take a UK produced show, replace the British voice over with an American one, slap another--albeit very similar--name on it and present it as an original production. Nazi Mega Structures becomes Nazi Mega Weapons. PBS or NatGeo gets to call it all new original programming when, in fact, they had very little to do with it.
They did the same thing with a show called Generals at War, except over here in America it's called Commanders at War and features an American voice over.
It has to be a money thing. I can't think of another reason why they would go through so much trouble.
who cares about the accent