They do fly in regulated airspace and they do not squawk or communicate with ATC. Sometimes the only way to tell their position is from the squawk of the escorting fighter(s).
It is a big problem when they go from one FIR to another as ATC requires height, point of entry etc and this cannot be provided. That said, over the last 30 years they have rarely caused any grief, apart from the nuisance value.
They have not breached territorial waters to my knowledge and they remain in International Airspace at all times. The fact that NATO designates some of this airspace as a Policing Area makes no difference.
Despite the hand waving of the Daily Mail the recent flights, and intercepts, are very common. If they were.nt, I would have been made redundant years ago......
As an aside, it is only when you read newspaper reports that cover a subject you know about that you realise what a lot of utter rubbish is published as so called
fact.
Better still is when you read the associated comments from so called experts that you also realise there are indeed some very strange people out there.