This question has been troubling me since the accident, hopefully someone more knowledgeable of ATC than myself can resolve it for me.
Was it not the case that the Tupolev had been allowed by the previous sector to cruise at a non-standard level?
That being so, on transfer to the sector in which the accident took place, should that not have been made clear to the receiving sector?
Naively, I would'nt have that you'd be handed over to another sector at a non-standard level without either their acceptance, or an instrution to adjust ( climb/descend ) to a standard level for the sector you are entering.
There are many areas of the world where non-standard level cruise is widely-used, and indeed encouraged. I've used it myself on several occassions, but always in the perhaps misguided notion that in addition to TCAS, we enjoyed this further protection.
Any thoughts?