Project Managers often want to check on progress. By maintaining a Project Master Model (similar to the Area Master model) this process can be simple and will become the basis for project reviews. The Master Model is created by creating a model file that Xref's ALL the Area Master model files. By following the rules stated earlier as to when to attach Xref's and when to overlay Xref's, circular references can be avoided. Here is an example: 
By simply reloading the Xref's at certain times in the project, you will have a project Review model which can be exported to Navisworks.