yup, I commute at -10c, but not for long, and find folks who bike tour in such weather to be very hardy souls indeed.
So Mr or Mrs Singh, are your bikes good and solid? Will you have the space in panniers for all the bulky winter clothing, and the usual extra space for food, water and all that stuff that such a tough trip will require?

what is the route plan?
when is the trip planned ish?

lots of questions, but an exciting trip thats for sure. Definately, lots of planning and logistics required.
I recommend at least 2in 45-50mm wide tires for all the rough roads you will encounter.

Oh, in case you do not know of this website--check out Crazy Guy on a bike, there are many trip journals of people who have ridden through the "stans", and will give you lots and lots of very good information on all aspects of travelling there.

good luck with your planning and prep.