Why would you need a neutral run from the center-tap of the wye generator to the ground point? From a fault current perspective, grounding the center of the wye to a ground conductor that runs back to the ground point in the transfer switch should suffice.
Center-grounded delta is better than an ungrounded delta. Floating deltas can be dangerous, as unbalanced loads (and single-line faults) can float the delta away from ground and activate TVSSs, which would cause a big fireworks display. Delta-connected equipment itself really shouldn't care if each leg is 0V, 480V or 600V potential from ground, just that's it's 480V phase-to-phase... though the insulation might care about ground potential, and that's a risk, too, when it's all only rated for 600V.
