As far as I know it is virtually imposible to fully reuse 3D geometry among diferent Solid Modeling systems. The reason is that the history tree, relationships and all this internal information that allows the program to manage the geometry is almost lost in the transfer.
The only exception I know is SolidDesigner, from CoCreate Software. It can read and fully modify any solid model (or even surfaces) coming from any other applications. Any change is possible, without any restriction, like if the model had been generated by itself.
The reason is that SolidDesigner is not a "history-based-parametric" modeler and can work directly on the solid geometry.
We have read a Pro/E model that had been saved in IGES and then modified complex fillets. But it can read direct native formats.