There is already a thread running on this subject and I think the answer given there is is that provided they remain in international airspace, they can pretty much do what they want - but with both their radar to protect them from ramming into a transatlantic Jumbo and (at least in the area where they are probing our defences) and ground based radar that can spot them at FL 360 there is no real danger.
"Without warning" is not the case as somebody will have been tracking them since they rounded the North Cape .. a good 2 hours flight away from our airspace.
http://www.pprune.org/forums/showthr...ht=bear&page=7
This long running - but with a load of recent posts- thread has responses from those far more knowledgeable than I.
DGG