https://www.gov.uk/government/public...bs-and-the-cps
This may explain the relationship and the agreement of sharing factual information between AAIB and the police or CPS. Therefore, I am presuming that the police want a copy of statements/interviews, as they should have the all the factual information to date already and shouldn't need a court order.
However, obviously a detailed examination of the wreckage and testing will take some time and this is maybe the part that hasn't been completed yet by the AAIB hence why the final report hasn't been published yet.
Interestingly, this is similar to the Glasgow helicopter incident only difference is that the pilot survived in this case, so could be prosecuted if it was deemed he was acting without due care and consideration and endangering others.