Three days before opening of official U.S.-Russian consultations on the new arms control treaty, Sergei Ryabkov, Deputy Minister of Foreign Affairs, gave a detailed interview in which he talked about details of the Russian position. Nothing particularly new, but this detail was interesting - asked about the future of the Moscow treaty (a.k.a. SORT), Ryabkov categorically said that this treaty cannot exist after expiration of START: "Without START, the Moscow treaty is a meaningless text."
While the Moscow treaty is supposed to rely on START for verification procedures, I don't think that it is technically correct to say that the Moscow treaty does not exist without START. It has a separate ceilings and its own counting rules of sort - the "operationally deployed nuclear warheads". Of course, Russia never liked this concept and never accepted the U.S. definition of it. This probably explains why Ryabkov was so emphatic about this issue - he is concerned that when START is gone this would be the only "legally-binding" definition that is out there, whether Russia likes it or not.
I would say that this proves again that keeping START with its definitions and rules in force is actually good idea. Russia should have thought twice before rejecting the option of extending the treaty.