Check for an existing wayleave, if there is one, check the area covered. It’s likely that a new or modified wayleave will be required to accommodate the stay.
Some pictures would be useful so I can see what sort of powerline is being supported.
I assume this is a through feed and doesn’t supply just you.
Is the property freehold or leasehold?
It’s unlikely the pole will be going back in the same hole. Some old pole were planted in big holes with cross members bolted to the bottom. New poles are typically augered in next to the existing one and the old one cut flush.
Ask for a method statement first with these sorts of details laid out on them.