Metal conduit is an acceptable equipment grounding conductor. Your transformer will constitute a separately derived source, and will need to be bonded on it's secondary neutral to the enclosure and to building steel and to any metal water pipes in the area served by the transformer. It might be a good idea to drive a couple of ground rods too.
The neutral in the 480 volt panel should not be bonded.
I would run an insulated green equipment grounding conductor in Greenfield (Along with the circuit conductors) to and from the transformer, attached to bonding bushings at the four ends.
In the transformer, I would continue the grounds to the neutral lug(s) or buss. The building steel, water pipe, ground rod grounds I would also connect to the transformer neutral lug(s) or buss. In the 240/120 panel I would have separate neutral and grounding busses. The ground from the bushing would extend to the ground buss. That may be the only wire terminated to the ground buss. The insulated neutral buss would terminate the neutral from the transformer and all branch circuit neutral conductors.
