I can't see why they wouldn't of put the ground lug inside the fixture, this just looks stupid. I'd of though the fixture would of come with a ground screw or lug from the factory.
We do...my R47 was 120/240v but the electrical codes here require ballasts with phase to phase input (208, 240, 480, 600V) to be CWI so I guess that's one of the reasons why 347v lighting is more popular, especially on building with three phase.
And I hope that ground is tight, this is a 347v fixture.
There's also 277/480V common in USA.