I have an incredibly fast bike (CdA of ~.2) and I can't get anywhere near that.
in "real world" (always windy, rough roads, and a couple rises that drop you into the mid teens) conditions, I see about 26-27 mph on 275.
example (both directions, same bike, similar conditions): http://app.strava.com/segments/4157197 (26.5 on 287) http://app.strava.com/segments/2594326 (26.9 on 268)
On a nice smooth track I've seen 27.5 on 285.
On my road bike today I saw 22.5mph on 253 watts out (on the MUP) and 21.1 on 230 back
2 layers of wool, some wind, fairly aggressive position, aerojacket (don't ask), I'm ~150lbs