Originally Posted by jrickards

However, my city generally experiences winter temps in the -10 to -20C (16 to -4F) range and I am wondering if these high end brands are capable of keeping a cyclist warm in these temps.

On the other hand, it is rare to see an amateur/pro road cyclist (live, photo or video) riding on snow- and ice-packed roads so it might be that high end cycling-specific winter gear (again, Castelli and the like) are designed for winters where the overnight temp might drop to -5C/23F and sunny, daytime temps go up to 5C/41F and any overnight snowfall has melted from the roads in the sun by noon.