Why divert?
Quick FlySmart calculation with an A320 CEO ldg (without knowing the actual weather/conditions at OMSK), assuming 10 kts tailwind, temp 15, QNH 1000, and RCC 5/5/5 (wet) at MLW 64.5 tons, with Green system reservoir lo lvl, gives an actual landing distance of 2148 meters.
There must be more to this story, or why on earth would they even contemplating diversion? A single hyd. failure on the 320 is not a great concern at all.
Regards.