Some time ago, I asked in SketchUp forum whether there was a way to explore and download the 3D models they propose on 3D Warehouse from a program, but I never got an answer [:(]
Nevertheless, I tried on my side and found how to do it. But now, Trimble permits to download 3D models only by registered users, probably meaning that they want to limit this traffic.
Maybe waking up the subject I started in SketchUp to get an official answer could help to get an official answer.