You have not given us much to go on but if it were my project I'd render out all of my elements in a 3D app with separate renders for lights, shadows, diffusion, specular and so on and then put the 3D scene in AE for final compositing and color grading.
If you are trying to insert CGI into video footage shot with a camera there are a lot more steps.
A still image or example video of something you are trying to replicate would help us point you in the right direction.
For the benefit of those unfamiliar with what you're talking about, the name of the Video Copilot plugin is Element 3D. You are referring to a package of preset 3D textured city buildings for that plugin called Metropolitan.
Beyond that, I'm not really clear on your goal, like Rick. Do you want to comp Element 3D components into live footage of traffic? (Sounds very difficult).
Do you want to create 3D traffic components to add to the Element 3D scene? (Not impossible, but it will mean getting some good quality 3D car models with textures, then incorporating them into your project, either within one iteration of Element 3D, or onto a second layer who's Element objects don't intersect with the first.)
Element 3D can do some amazing and impressive stuff, but can be surprisingly limited when it comes to working with multiple 3D models in one space.
It might be easier to just shoot what you want... depending on what you want, of course.