PJ,
I know nothing about flight data analysis, hence my posts only ask questions on the subject.
What I would speculate is that if data was to be made available then maybe someone sharper than me with access to specialist software/skills might take a look and run analysis. These might be industry professionals, software companies, academics etc. Who knows they might contribute something new to the incident/safety, use it as a case study or corroborate the BEA. What harm could it do?
Perhaps the reality is that the legal council for the stake holders would throw a fit so we are probably wasting time talking data sharing.