According to
this report Russian airlines are carrying on operating their 737s regardless.
The article goes on to say:
"Russia’s Federal Air Transport Agency has refused to budge, saying it alone is empowered to halt foreign aircraft operations in the country and the committee, known locally as MAK, lacks the authority to issue such a ban. The agency’s chief, Alexander Neradko, said MAK revised its earlier statement on the Boeing 737, and Russian authorities see no reason to call for parking the single-aisle planes."
It all seems like internal politics and nothing particularly to do with the 737.