JAR/EASA permits this sort of operation, and for pilots to be on the flight deck of an airliner with less than 200 hours; look there for your problem.
Hmm, IIRC none of them had less than 200 hrs...so...?
Should they have asked questions and dug deeper? Of course they should have and that's where they're going to be exposed in the courts - duty of care and all that, yessir.
Should they really? So they charter an outfit that has an AOC and should firstly ask operation related questions?
Bollocks, me thinks. THATS why there is an AOC. Proof that you have standards, an organization suitable etcetc.