Can electric utilities turn off entire areas with the flip of a switch?
 

Saw the press conference with Hawaiin Electric. the President and CEO stated that Hawaiin Electric was unable to power down (de-energize) the grid and that the water pump stations required electricity so they decided to keep the power on.

So, how fast can an electric utility turn off power/electricity to a given area, sub-division, etc. in an emergency?

I can answer with some authority. A neighborhood could be shut down pretty quickly. The larger the area the more time it takes to deenergize due to having to coordinate with generation and transmission. There are hundreds of operations required for a large scale de energize. Turning the power back on is time consuming as every circuit needs to be physically inspected to ensure it was not damaged while de energized. Not knowing the area it's hard to say.

They managed to turn off the power to the water pumps early on in Maui, , , , ,

That was not an electric issue it was to preserve fresh water. ( and a wrong dumb idea ) The elec co didn't shut down the power in time to prevent the start of the fire. But yes, we have the tech to shut down your service and any thing above that, including nation wide, should it be deemed appropriate, get a generator.

I knew a guy who was responsible for the safety of an area in case of a disaster.

He could shut down the cell phone system to allow the average person to only text. This saverd all the voice bandwidth for those emergency folks that needed the system to save lives.

And he didn't have to check with anyone. He was the guy who made the decision. From an emergency responders standpoint all would seem normal as their phones would work. For the rest of us we would get a service unavailable notice.