I just started downloading a few BAT files, but some of them (like the world trade centres) just apear as huge cardboardboxes when I plop them down. Does this mean I don't have enough jobs to build them or did i screw something up?

Do you have the Rush Hour expansion pack? You need that to have BATs show up. If so, I would suggest downloading the Sim City 4 Update http://simcity.ea.com/coolstuff/bat/index.php