If I remember back to previous vray versions you could create the original mesh from the proxy settings.
Is this a hidden feature with the new proxy in vray5?
Refer to this topic for the answer.
Updating this thread here too:
in the latest stable builds (version 5.10.20) you can import the mesh from a proxy in Maya by using a script command.
vrayImportVRmeshGeom <path/to/file.vrmesh>
We’ll publish documentation for this soon.
Hope this helps.