Nest of squirrels?

The question mark arises from their location. I found them inside of an electric sign board, mounted onto the face of a billboard my workers and I were replacing at about 85' above ground. I found them after the crane had lowered the sign to the ground and I heard them chirping. Can a squirrel climb 80' vertical of either the flat iron of the access ladder, the conduit(2" smooth), or the 5' diameter column?

The mother had come back by the end of the day, when we were loading the old signs for hauling. I "know" this because when I relocated the nest and babies to nearby tall weeds there were only 5 of the original 7. I had also heard cheeps on subsequent trips back to the ground.

Work camera specs, Canon PowerShot A1100 IS
( I still put my face up to the camera every so often. I'll never get used to P & S!!)