That top speed is also after riding for 6 to 8 hours straight. Certainly they can hit much higher top speeds even riding alone, than the rest of us, but the speeds you are refering to are achieved through the power of the Peloton (drafting). All of the top sprinters have lead out riders on their teams that run at the front during the final stages of the sprint, pushing the pace and providing the final draft for their top sprinter to use to slingshot across the line. The lead out usually begins around 10 to 15k out from the finish, but the final burst for the line happens in the last 200 meters or so.
As an example of the power of the mass draft, watch how quickly the Peloton can reel in riders that have broken for the lead ahead of the pack. Sometimes these riders will make their breakaway early in a stage, lead for 70k or so, build an 8 minute or more lead, then get caught by the Peloton within the last 1000 meters.
Bicycle racing at the highest level is tres cool!