thehog said:
...The data says its not possible. ...
That's not really a conclusion that you can draw from the historical evidence.
Just because it hasn't been done, doesn't mean it's not possible or even, not likely.
You'd also need to look at the setup of cycling in the different countries and how junior development programs work.
I know the Australian system fairly well and I think it's the type of development that is very likely to occur in Australia, because juniors are encouraged to try multiple disciplines and keep with them for quite a while.
Many of the Australian pro riders for example have spent a long time on the track: Renshaw, Brown, Mathews, Hayman....(and many more).
Even for other road riders, a lack of evidence of their transition could result from an early cross from track to road, simply because the rewards in a road career are much greater than a track career (except for very few like Hoy, Meares, Pendleton, etc.).
Outside the Oz setup though, I'm not sure how other countries have their dev program setup. It may be that they run different road v track programs for different riders without much cross over, so there aren't the same type of opportunities for riders to succeed on the track and then progress to the road after that.