I think winterization is more to do with equipment, then with men themselves.
For example entire division of this guys
http://en.wikipedia.org/wiki/Panfilov%2 ... _Guardsmen were formed in southern desert part of USSR (Kazakhstan), so they are not like northern people at all.
And still they fought exceptionally well in battle for Moscow.
Many other USSR army formations had nothing to do with "people grown up in cold regions" aswell, since country was large and multi-national.
Also weather in european part of russia (where action often takes place in CEAW) is not really so harsh, as in Syberia. (Not sure about WW II times, but now its only couple of weeks, when temperature is ~ -20 C, often its pretty comfortabe and closer to -10 C.) And winter in western areas like Ukraine/Belorussia/Baltic states can be even warmer.
I think in winter 1941 soviet troops suffered all same problems, as germans did, thanks to outstanding cold winter, but they didn't have to move so many heavy equipment for so lond distances, since they were on defence. Also soviet tanks/planes/trucks had better generic level of performance at cold weather (not ideal ofcource, but better then most german)
In winter 1942-43 in Stalingrad battle german troops were first of all out of supplies, so influence of winter was not so great. They would suffer from lack of food/ammo/medicaments any way. And Romanian/Italian troops (who's poor performance was the reason of Stalingrad pocket) could be easily defeated by soviets at good weather aswell.
Winter 1943-44 was rather warm, but german army was already in terrible fighting shape, after lost battle for Dnepr.
Severe winter (and other things, repeating in german general's memoirs, like stupid Hitler who always ruined their brilliant plans) is only partly reality, but partly a myth created by themselves to justify their erorrs.
Yes german troops were totally unprepaired for winter in 1941, but who's failure is it? Didn't their leaders had common climate map, which every schoolboy can look at? Didn't they know that it may be cold, if you stuck in Moscow outskirts in December/January? Didn't they know, that fanatic soviet people will keep on fighting, even if germans enter Moscow?
So I think role of cold winters is a bit overestimated, when overlooking war on the east, but in game current concept going well, allowing soviets to mount effecient winter offencives. I think its some abstract concept, and its working OK as it is.