The crews at the Didcot Railway Centre in the UK released this tidbit of info this morning; as of June 22, their steam railmotor is now certified for mainline running on select parts of Network Rail. Full report here:
http://www.railmotor93.org/latestnews/latestnews.html

Thanks for the link--it's a most impressive example of preservation and restoration. To a traction fan like me the first impression is "Wow! A steam-powered interurban car." Just one more reason to visit the homeland of railways.