If you make this part of a SourceMod plugin you'd have to distribute it with your map. Also I'm not sure you can really do what you need to, because the movement is built in to the game engine. It's 'Q Physics', or the basic physics engine (not VPhysics) that is responsible for the movement of brushes and player collision with them. I don't think you can manipulate it to such a degree using a server-side mod.
Crash's link is the best built-in entity to use because you can send an input to the rotating brushes asking them to rotate to an exact position. If your poster segments are square, those positions would be 0.25, 0.5, 0.75 and 1/0. But steve is right, that kind of thing is typically seen in dynamic props because it's far more efficient, so if you can do that in a 3D program like Blender, that'd be the best solution.