This question is similar to How can I randomly power one of several wires in Minecraft?, but uses command blocks and only 3 outputs.
I'm making a Minecraft server and it has three different hubs that one can spawn in when they join the server. Each hub is identical. When a player joins a the server, they spawn in a 1x2x1 box. This box has a pressure plate on the bottom. When the pressure plate is triggered, I want to be able to randomly select one of three hubs to teleport to. Is it possible to do this through command blocks? Or will I need to make a redstone device?