You still need to be prepared to spend an time standing around off the bike fixing a mechanical or waiting for a ride.

Just like ski touring, having an extra warm layer to throw on is a big help.

for genuine survival, a great piece of winter equipment for a bike kit would be a silnylon cagoule (Hilleberg) or any other makers' cag, coupled with a down vest. Probably make them fit in your jersey pockets if you're into that kind of thing.

And wearing wool really cuts down on the evaporative cooling effect so commonly felt in synthetic workout clothing.