I'd say they are permanently part of the truck. The large spoked wheels are how the ladder was extended. These are from before hydraulics were made small enough to be used like they are today. Turning the wheels by hand would move cable/ropes that extended the sections of the ladder. The truck looks to be from the late 1920's or early 1930's.
Nope, they used to roll em off the back of the truck, down the street and into place against a burning building. They used ropes to extend them, I think the later ones had a hand crank on them too