It seems pretty clear
- Authorized Uses
The license to the Models granted above is limited to:
- Incorporating or including Models and Creations into a larger work or a deliverable for a third party ( “Combined Work” ), provided that the Combined Work includes substantial additional content to the original Model;
- Distributing Models, Creations, and Combined Works to third parties for your business purposes (including for commercial purposes);
What you must not do is to claim credit for somebody elses model, or remove their author information.] And you mustnt sell models from the 3d warehouse if you have only made minor alterations (eg if you just open it and change the color.)
what you are making with your city is substantially differnet to the 3d warehouse model
That being said, it woudl be best for you to take the 3d warehouse models and customise them as much as possible; not only will this make your creation better and more unique, it will probably inprove the modeling quality and consistency.