A recent appeal court decision in 2013 relating to a fatal in 2011 confirmed that AAIB reports are admissible as evidence in any court proceedings.
I think we can safely say that one way or another this accident will result in court cases.
Without wishing to appear pedantic, at present an AAIB report is not admissible in "
any court proceedings" - the decision related to civil proceedings not to criminal prosecutions. But you are still correct to suggest legal representation during either AAIB or Police interviews.