It's a bit of both. I did a simple model - just boxes basically and painted the textures in ortogonal view. I used that to get it somewhat into perspective. A lot was added and repainted afterwards so it is not entirely 3D.
Thanks for the encouragement guys.
I've put together a new matte painting reel, that features works done for some feature films and TV shows that I've worked on in the past. Access it by clicking the image below.