The most shocking aspect of this event, is that if it happened to an SAA crew at FL120, it could happen to anyone - or me.
The investigation questions are obvious;
What was a heli doing at FL120?
Was either crew cleared to be there?
Controlled, or uncontrolled airspace? Was it see & avoid?
IMC or VMC? (CAVOK by definition does not apply above 5000').
See & avoid in a modern airliner is an uncomfortable position to be in. Closure speeds are too great, and even looking for an other aircraft where you know its position can be difficult.
They were very lucky not to loose both airframes, but I guess sometimes fate is on your side.