...a 30 kt ram into a concrete wall with no fire is hardly going to render them unreadable!
Of course not - but first things first. The external condition (including pre-existing anomolies) needs good documentation - to see if any internal or data defects can be correlated with external condition.
At least that's the way it's supposed to work.
More of concern I'd think - to ADAT (GAMCO) anyway - is permitting French authorities to read out the recorders. Remember the Cameroun accident w/Kenyan 738 jurisdictional issues?