Jens' Trek track bike uses a custom rear cog (and perhaps the bike is considered custom too). Doesn't equipment have to be available for purchase by anyone? Also new frames and forks have to be approved by UCI. (Of course I'm sure Trek will sell me a comparable frame/bike if I offer them enough money.)
"Bicycles and their accessories shall be of a type that is sold for use by anyone practising cycling as a sport. The use of equipment designed especially for the attainment of a particular performance (record or other) shall be not authorised.”
Source: http://www.uci.ch/mm/Document/News/R...NG_English.PDF
I wish Jens all the best in going for the hour record.