There is propably a robust work around and tha is .DNG. Please take a look it may may prove to be very useful.
Autodesk and Bentley to Advance AEC Software Interoperability http://www.bentley.com/en-US/Corporate/News/Interoperability+Agreement/Autodesk+Bentley+Agreement.htm
OpenDGN http://www.bentley.com/en-US/Products/MicroStation/OpenDGN/