They're likely to be normal plasmas if mounted on their own. You just ensure that what you fill the plasmas with is suitable - either by shooting it at 90 degrees - for which you can buy special camera mountings - which I think the BBC may have used for one of their previous Washington sets, or buy shooting normally and cropping/rotating - though in 16:9 this is pretty tricky.
I'm sure I heard something about how they went to the effort of shooting the Washington backdrops at 90 degrees, then whoever was mastering the DVD heard it was going to be used on a plasma at 90 degrees, so rotated it again with a DVE. This may, of course, be apocryphal.
Yes, they could spend a load of money on LED numbers which can be reconfigured, or they could spend 0.01p on some new numbers quickly bashed up in Word and printed out.
As the person in the office who usually ends up ordering the stationery, can I ask where you're getting your paper from at that price?
I imagine that like any office, once you're behind the cameras you'll have all the normal trappings of a professional office, complete with in jokes stuck up on the walls and that annoying person who wears a Simpson's tie everyday in the fleeting hope that people will think he's hip and trendy.
I work with some people who regularly print out Dilbert cartoons and pin them to the wall. (It always surprises me to find that Dilbert's still going.)
I know of one control room which has a wall of shame - screengrabs of their colour bars on air. Or other people's colour bars on their channel. I think there may be bonus point for their colour bars on *other* channels...