I brumate (hibernate) some of my adult Testudo, including Russians. I keep others active throughout the winter months. The only difference between those that brumate and those that stay active that I have experienced is that those that brumate have a more consistent breeding pattern. Those that I have that stay active do not nest at precise times of the year as the brumating tortoises do. But in both cases fertility rate is the same.
It's been my experience that Russian tortoises are triggered to breed more by abrupt and extreme changes in temperatures and light intensity than just by brumation.