Bentley AutoPLANT is based on AutoCAD and as such uses the DWG file format to store model geometry. Any settings related to the DWG file format also affect files from AutoPLANT.
AutoPLANT Object Properties can be stored in external database MDB files. By default, Autodesk Navisworks also supports these files through the DataTools functionality, and looks for Equipment, Nozzle and Piping datatools links.