But there must be some sort of portable alternative that could be rigged up to cool the cabin at a significant energy savings.
Also worth considering how and why the trucks end up idling. Is it a few minutes here and there or do they park and wait to be loaded for longer stretches?
I was thinking they could add an auxiliary battery that runs in-cab climate control. Considering those trucks are made to haul 400 tons and cost $5m a piece, this would be a no brainer and not affect the cost or hauling capacity in any meaningful manner. Their fuel economy really is that bad from what I've read. 5 mpg would be a pipe dream. Long haul tractor trailers get about that while loaded, and they weigh about 1/8th of one of these loaded and aren't driving on rough dirt roads at sub-optimal speeds. I don't think he was exaggerating the fuel consumption.
As for the necessity of AC, it can't really be avoided in a pit mine in W. Australia. It's unbearably hot. The cab of the truck could hit lethal (heatstroke inducing) temperatures if the windows were closed in that environment.
Either way, it really wasn't meant as something to overthink. Just one of those interesting useless tidbits of info I thought would entertain some folks.