Victor Belenko's Narrative of Blackbird Activity in Soviet Far East

In the book "Mig-Pilot"
The ghost author writes that Mig's were Scrambled
to intercept Sr-71's that flew just outside of
Soviet Airspace in the mid 1970's.

The Blackbird's allegedly would "scoop up to altitudes
that the Mig-25's couldn't reach or dash off at
speeds the Mig-25's couldn't match" ...as they
played with the Ruskies.

Is such an encounter possible? I thought that
the Blackbird pilot was rather busy shooting
film and getting ready for the next fueling.