The AIB at the state of occurrence will be in charge of the investigation, in this case the GCAA.
Now the AIB is supposed to be impartial but in the UAE it is organized under the governing body of the GCAA - This is in my opinion a problem!
In most countries the AIB is completely separated from CAA to make sure that an investigation will be conducted without pressure from the governing authority.
Who owns Emirates, who owns the GCAA and who controls the AIB?
Lets see how they can spin it!
That said Boeing, RR and probably the ATSB will be accredited to the investigation.