You can do that, but you need to be there or someone has to be there to help the guy with the body up and signal him, its really kind of hard to see that while in the cab of the truck, or judge distance.
The things people don't think of do happen. I was placed on some old junk excavator, an Insley 1000, years ago on a road job, stripping blacktop, under electrical wires, and the control linkage broke, jammed, the boom kept going up, I could not stop it, I jumped out and got away from it, it ended up into the wires and arc'd out, who would have thought, controls stopped working, something goes wrong and you are too close, which we were with a machine that should have been scrapped out.
On the other end, think of what its like to be a driver, I had this dozer operator who worked for a large outfit who hired our trucks, they were doing site work, we were hauling top soil to them, heavy topsoil, and he'd have me back into dangerous places with a freightliner tri-axle, with a 20' body on it. Soft, uneven, got to the point on every job, he'd keep waving me to come further back, this and that and I told him no, he got really ticked off, and we were headed to get into it, no way I was turning that truck over, drop was close enough for him, he was greedy.
If there is enough room to get behind the wires, its ok, but someone needs to guide the driver, its a dangerous combination and one slip or mistake doing this, only reason I mention it, most drivers will consider it, but it sucks to have to trust a brake, get out of the truck, with a body up and check how close it is to electrical wires, having a set of eyes on the ground is a nice gesture for the driver.