Depends on the exact license terms. Many models that can be normally bought on 3D asset sites can be distributed further only in a format that cannot be converted back to the original model in a way that would allow creating derivative works. In that regard distributing the Outerra packages created from these models is fine.
For Google 3D Warehouse models - the original submitters gave the license to use/distribute/whatever just to Google, it doesn't mean that any other entity gets it as well. Regarding the users of Google services there's a clause that allows them to modify and distribute the uploaded models, but only for the use with the Google service.
So, unless the model has an explicit license allowing the use elsewhere, it's not generally allowed without a permission. Certainly not for a commercial entity like us, although modders may be able to exploit the "fair use" under certain conditions.