Is Polar Lights observation possible at the latitude of 56° N?

Yes. The Aurora form in a ring, roughly centred on the Magnetic pole. The pole does wander slowly, but it has been located in the Canadian Arctic for some time.

As the pole is on the American side of the Arctic ocean, aurora are seen at lower latitudes in America than in Russia, nevertheless, when a powerful solar storm occurs, aurora can be seen at surprisingly low latitudes, even into the subtropics, as Wayfaring stranger notes in her comment.

Aurora in Moscow is a notable, but not exceptional occurrence, as this news report indicates http://www.themoscowtimes.com/article/507096.html