Thanks to Mark for some helpful pointers

Regarding reference shaders: at least as of Carrara 8.5, one needs to turn off the global option, under Preferences->Shader Editor, "Automatically Create Mapping Shaders for object." This setting could change alot of imported shader appearances as well, depending what you are importing.

Also, if you dont turn off 'preferences->common file load settings->consolidate shaders on load' Carrara will otherwise politely remove all your work as unnecessary:)