The engineer(s) were commissioned by the Chief Pilot of the operator for insurance purposes.
They actually visited the crash site when the snow melted and found one engine was not running at the time of impact and that the propellor was feathered. How the ATSB worked this out, I don't know. They didn't even see that one of the propellors was actually in practically perfect order?
QNH 1013.2: That quote from your last post sums up the problem with the engine failure theory. The Chief Pilot wants to shift the focus of the findings to mechanical failure and not on operational issues. The Chief Pilot was well aware of the procedures that the accident pilot was following and witnessed the pilot using those procedures on the earlier flight into Mt Hotham.
The statement about visiting the crash site after the snow melted is also flawed as the propellor in question was not in the as found postion by that time. I'm not sure whether you have read the final report as well as the supplemental report, which was issued after the intial allegations were raised about engine failure, but they were both very clear that the propellor blades had separated from the dome due to the impact forces. This means that the blades were not attached to the dome and could in fact be photographed in an apparent feathered position. The photo that was published on pprune was not convincing evidence of the engine having failed prior to impact. The final report also provides a lot of detail about other evidence that indicated that the engine was producing power at the time of impact.
The fact that the pilot who took the photo was an experienced helicopter pilot is irrelevant if he does not have any experience in accident investigation. As watching "CSI" does not qualify you to be a Detective neither does watching "Air Crash Investigation" qualify a person to be an air safety investigator.
At the end of the day it was an unfortunate accident that could have been avoided.