Your post reminds me of conversations I've had in the USA with friends. They can't understand why Cambodia has constant power outages but yet cell phone coverage nearly everywhere and access to the internet at affordable to anyone rates.
I always explain that in the USA we're plagued by old and outdated infrastructure that is costly to keep going and in many cases almost impossible to replace because of the logistics involved. When I lived on the Vietnam border, power cuts almost never happened, and only when Vietnam needed to cut us off during peak usage so they could meet their own needs.
I was not aware that a place existed in Cambo where Vietnam was supplying the power. That must be a complicated bill collection procedure.
I was wondering the other day why cell still works when power goes out, even planned power outages that affect almost the entire peninsula. As it turns out, cell towers have massive battery and generator backup that lasts 3-5 DAYS. According to one website I saw that if the power actually does go out for a cell tower it can be rather big problems for the company involved because rebooting is problematic and dropped calls means lost revenue. Basically it was more cost-effective for the company to ensure that these towers stay on no matter what.