Not quite one-way-doors, because I that would mean letting ALL players to pass from one side and block from another side. That isn't possible right now.
However 1.5.1 beta already has new polytypes that block players of certain team. So you can place a red-players-collide wall to allow blue players to pass through, but red players will collide with it like with normal wall.
Since 1.5.1 is still beta - I haven't seen any maps that use this feature (but I'm sure there will be a plenty. People are already coming up with some
really cool ideas).
I used those polytypes in some of my INF map remakes (in my sig) to prevent spawnkilling.