The out riggers on a utility company backhoe would seemingly have hard rubber pads for street work. Typically stacks on ends of tire sections or something similar, like a rotary mower tail wheel. Even if a T shaped steel cleat is on the bottom like some do have, I don't believe, (and I am going off from what I have seen on job sites) that would suffice if the backhoe was energized. Right here on this property, when they did some upgrading of the power lines, one new circuit as well, whenever there was any substantial piece of equipment working in reasonable proximity or what is the safe working distance from just the 30,000 volt lines, a copper clad earth ground rod was installed to full depth, a lead with a heavy and strong clamp was used to make a connection to a track pad or some substantial part of the equipment, seen it with excavators and hydraulic cranes, probably have a photo of it too. There are 115V lines running through as well, they were not near those. I'm sure someone else with experience in these matters would know more about it, but I've been around enough line work, 15KV splicing and lots of other things to know better than to take any chances at all. If that live conductor contacts that hoe, its going to arc off big time, has the potential to blow the tires out with pyrolysis and obviously the operator may not fare so well. I saw a fatality in this town when I was a kid, material supplier boom truck contacted primary wires, killed the driver, I can see the building from my house. When I was a young heavy equipment operator, I narrowly escaped a similar fate, was in an old Insley 1000 excavator with worn out control linkages, one of them came apart, jammed and the boom and stick kept going up, I could not get it free, I jumped out, let it go, given the position and where it jammed up, no time to even think, like shut it off or what, I leaped off and the boom went into the overhead power lines, it arced off with a big blue flash, energized that old hunk of junk that was on pavement with steel tracks. This was on a road job and we had to work under these low un-flagged or protected lines. It was one of those companies with poorly maintained equipment, even their later model trucks were junk, I left them because of it. So maybe I'm a bit apprehensive, but with good cause.
LOL! I'd not worry about any arguing, just for discussion, and maybe I am way off here LOL ! but I am safety conscious when it comes to any kind of electrical power. Lets see what others say, lot of electrical knowledge here, my comments are just based on observation and more opinion than not, though I have been around line work and electrical distribution on job sites, closer to it than I'd have liked at times too !