I stick to 3 season touring so don't anticipate experiencing anything close to freezing, but I have tested out my tent, pad and sleeping bag on frosty nights in my back garden just in case. I was ok in my 40F bag, wearing socks, long johns, and a long sleeved top. IMHO the lightweight approach could be successful in winter conditions with a few gear changes and a bike with fatter tires than my Cervelo. You might want to beef up the tent a bit as the Contrail is single walled.
I usually take a Marmot Driclime Catalyst jacket as my insulating jacket for 3 season touring. If I was expecting it to be really cold I'd replace it with a down jacket.
well when funds allow i will need a new down bag and matt i'll stick with the tent i have i think 2 person mountain hardware spear 2 heavy for lightweigh i know but have you seen the price of tents madness.