whats up with tranzit on black ops 2?

Firstly you can build these things: A turbine (portable power generator) in the spawning room, a Zombie Riot/Assault Shield in the diner, a Lawn mower thing in the farm, an electric trap ( like the ones in BO1 but you'll need a turbine to power it) in the power plant, and the Thrustodyne Aironautics Model 23 (the Jet Gun) in the bar in town. Lastly you can also add parts to the bus like a ladder to get to the roof from the outside, a ladder to get to the roof from the inside and a part that goes in front of the bus that kills every zombie it hits. All of the items exept the jet gun and the bus parts are in the areas where the crafting tables are. The other parts are in different locations. Since this post is getting long I advise you to check a YouTube video. Sorry for the long post.