[Sam Bauers]

If you upgrade to the latest bbPress trunk you will have access to the new BBXF exporter. There is also a standalone BBXF importer for phpBB, but I have not tested it yet. You will have to do some work to get it running at this early stage of development, this should be a lot easier as we move forward with this idea.

For more check here http://bbxf.org/