I planted 8 rhubarb seedlings last year (victoria, it said hardy to -5C on the packet) and 7 are coming up already, no covering , no protection, and this winter it got down as low as -18C here (excluding wind chill). I do know however many people that have tried and the plants just died, maybe dependant on soil more than weather.
I have 2mth old rhubarb seedlings available @ 4.50lv/plant (early red and glaskin's perpetual)