Using B gear in winter?

In North America, Primes and non-Primes absolutely positively have different batteries. I won't speak for your country.

The Prime also has a sprag clutch. The non-Prime does not.

The Prime is rated to go 80 mph in EV mode without overspeeding MG1 when the ICE is not spinning. The non-Prime's MG1 is so rated to only 60-something mph.

I know the transaxles and batteries here are different, at least on my continent. The part I don't know about, is if these differences are relevant to the title of this thread.

 

Getting back to the OP question as we are drifting into “b mode regeneration” discussion not as OP asked is it ok to use in winter. Since both ICE engines are the same (2ZR-FXE) and B mode primary function is to apply a moderate amount of engine braking both plug-in and non plug in act in the same way with regard to B-mode driving. Used with caution and not excessively it will aid on steep hills. Using Eco mode in slippery conditions is also useful as this reduces throttle responsiveness and a lower pull away speed. That said B-mode should not be used all the time as there is a cautionary in the manual that it may lead to extra stress on the ICE.

 

I took the OP's question to be more "is it advantageous to use in winter"—that is, does it confer some handling or controllability advantage?

I would answer "yes" to "is it ok" and "not so much really" to "is it advantageous", for the reasons already covered adequately in #2, #3, #4, and #5.