I think central banks generally give advance notice of policy changes. The Russian one hasn't announced any policy change related to the current fall, has it?
And it hasn't changed it. The Central Bank just isn't interfering in what's happening on the foreign exchange market.
Well, it actually changed the policy a little bit a few hours ago -- it announced that it stopped buying foreign currency until the end of the year[0] to reduce the pressure on the ruble. I guess that means that it doesn't want the ruble to fall below 110 rubles per dollar.
