First hand story from Russian ATC guy:
There was no interception at all, no jets.
The prolem basically is that ALL Russian airspace is controlled by militaries and only designated airways are controlled by civilian ATC.
The flight was coordinated with civil side through the normal procedures and in their turn Russian civil authorities should coordinate that with militaries. It is not known exacly where the system failed but militaries knew nothing about this flight. Further, when 777 entered Russian airspace, it was assigned with "intruder" status by military controllers, but apparently they realized that civilians know about this flight. Then they have relayed the ORDER to civilian ATC to turn the flight back instead of scrambling jet fighters. But do to the fuel onboard remaining and lack of suitable divertion airport in the area, civilian ATC decided to allow them to proceed to Moscow.
Typical Russian chaos