Yes you can back them out with a big pipe wrench.
For the guys talking about the hydraulic augers and the cost. I have mounted a hydraulic motor on several PTO post hole diggers. Just remove the PTO shaft and make a bracket to hold the motor. I usually direct hook them but I have also used two sprockets and a chain if my motor was not the right size.
I usually use the reel drive motor off a JD grain table. They can be bought used cheap and the rest is off the shelf stuff. Usually less than a few hundred dollars.
I have one setup that way on my auger and I use the same motor with different mounts to run an old cement mixer and also use the same motor to raise my silo unloaders.
So once you get the motor and hoses you can use it on several things and spread the cost out.