When it comes to low temperature performance for NiMH cells, it is safe to assume that the better the high current performance is, the better the low temperature performance will be.
With that being said, the standard 2000 mAh Eneloop has quite good high current performance, so it does not surprise me that it would perform better at low temperatures than many other NiMH cells. If you want better low temperature performance, you might look to the Elite 1700 AA cells. Although I have not tested them at low temps, it is quite likely the same design features that give them great high current capability would also give them good low temp performance.
So, my advice is to try the standard Eneloops, but keep a spare set of Energizer L91 lithiums on hand. If the Eneloops fail to satisfy, then try a set of Elite 1700 AA cells. Just be aware that the Elite cells have a relatively high self discharge rate, so you need to make sure that you top them off before you need them.
Cheers,
BG