In the 2005 LA Triathlon the top MPH on the bike split was 25.8mph. Tim DeBoom was 24.8mph. In the 2005 Chicago Tri the MPH on the bike split was 26.9mph - as I understand it Chicago is a pretty flat and fast course. These results are for male pros.
Can you really average 25mph for 40k? That is very very fast. Comparing triathletes, even pros, to state champion TT results or to pro cyclists is not accurate. A very very strong triathlete biker would probably be dusted by an average pro cyclist. Of course, the biker probably can't swim or run very well.