As far as I know PDMS cannot interface with SmartPlant 3D, I don't think anything can, PDS can't even fully interface with SP3D.
But you can bring in the geometry from the Mechanical CAD systems you mentioned using translators provided by AVEVA and also it's collaboration with Okino, who develop multi-CAD translators.
PDMS is not a mechanical CAD package, nor is it a file based system. Rather PDMS is a plant design and database (Dabacon) driven application. Therefore the is no File > Save As functionality. Aveva does have import and export applications for unintelligent AutoCAD and Microstation files. Again, they are seperate standalone applications, outside of PDMS.
