Since you're doing a modern tank car facility (as I rememeber), I'd buy some cheap containers and scatchbuild the office. You get more space and you can arrange them the way you want. Converted containers for office structures are so common now that it would fit in better for a small tank car loading plant. Those Kibri containers are nice but kind of expensive compared to getting a couple of $5 containers and just adding the windows and doors yourself.
HO Scale Modeler