I had this debate as an EC back in '05 regarding portable light towers. Diesel, 4-6 1000 watt MH floods, and 2-120 volt GFIs on board. (Towable units)
The AHJ wanted grd rods at each unit. I had 65 units spread out over grass, paved parking lots, quarry auxilary parking & a few municipal streets.
Discussions, and a polite request for an article number eliminated the rods.