Also goes the other way and I'd bet that Control tried to call them up multiple times on 121.5 with no response before considering to scramble the QRA jets. So my bet is that they did not have a radio set for 121.5, the volume was to low or they just didn't listen for the calls.
Furthermore, if they have been in german airspace before they should have wondered why they did not get handed over to the next frequency for such a long time, and maybe try to establish comms with privius agency, try on 121.5 or look it up in their flight pubs.
As I have found myself sitting in the cockpit multiple times during QRA scrambles towards "non-talkers", I seriously consider this pure airmanship when a crew of two pilots flying straight and level on full automatics at cruise altitude, are able to fly halfway across Europe without noticing that they should be talking to somebody.
Regarding the ethical dilemma of 1 aircraft full of pax VS many more people on the ground, I fully respect the germans with that regard. Main thing is that they have given it some thought before a potential incident takes place and that they have made the decision beforehand. Once the event is underway there won't be enough time to have this kind of debate.
http://www.allthetests.com/quiz31/pi...jpg?1436189258
I also bet that all other NATO contries have procedures in place for such a case, and that if a decision is made to bring down a civilian aircraft, this decision will not be a decision the pilot in the interceptor will have to make. This decision will be made in the highest leadership level.