I'm sure we'll soon see a detailed response from Marik.
This is a vast topic, so I won't be able to write detailed response at the moment. To put it in short and concise form, in my view the "Russian Piano School" is not even about geographical location, but more about certain qualities and values, such as a deep and singing tone, legato, special lyricism, intonatsia, etc.
In this respect I believe Rachmaninov, Horowitz, Igumnov, Flier, Goldenweiser, Boshniakowitch, are much more "Russian" than say Neuhaus, or Richter.
Moreover, in Russia itself there were many different schools and approaches to pianism. For example, Saint Petersburg was completely different from Moscow, and Odessa was very well known for an excellent technical preparation and many great pianists (of course along with great violinists, which came from Stolyarski School). Yakov Zak, Maria Grinberg, Emil Gilels, came from Odessa (but again, all of them were polishing they art in Moscow).
I have difficulties to call Mr. Peskanov's regimen "Russian" (even formally it comes from Ukraine, from the place with very specific training). Even bigger question would be: how it is different from, let's say, "French regimen" as presented by Mr. Duchable:
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Best, M