I've done airside transit at ADD connecting onto KQ (although not a straight turnaround) probably 3-4 years ago. OLCI didn't work for me, but I went to the Ethiopian transit desk (they were the ground handlers for KQ) and they took care of things.
Just grab one of the KQ staff at the aircraft as soon as you arrive and tell them you are connecting back on the same plane. They will sort you out.