Rowan did it in 2007 in France. This was our trip:
http://www.machka.net/pbp2007/2007_PBP.htm
Another friend of mine, Rob, did it in 2002. He cycled from Vancouver to Kamloops with his gearing set up as single speed. Starting in Kamloops, he did the Rocky Mountain 1200 (where I met him) on a fixed gearing. Then he switched back to single speed and rode across Canada and the US to Boston, where he switched back to fixed and rode the BMB 1200.