Has this been energized yet so that you can take some voltage readings to help verify exactly what you do have?
Is there three or four service conductors?
The fact that you said he used bonding bushings on PVC raceways does raise questions of what he may or may not know.
If it is a corner grounded system, they may be somewhat old school for services but are fairly common if you are using a separately derived system and are using a back fed delta-wye transformer as the source. All you have on the high voltage side of such a transformer is the three phases to connect to and you either have to ground a phase or use as an ungrounded system with ground fault detection equipment.
Otherwise it is no different than other grounded systems, except you need to forget the term "neutral" and learn the term "grounded conductor". NEC has all the requirements in the sections you are used to using all the time. The phase that is the grounded phase is also the "grounded conductor" and it is treated exactly the same as the grounded neutral is in a system that utilizes a neutral as the grounded conductor.
The grounded conductor is brought to the service equipment, bonded to the service equipment enclosure, and to any metallic enclosures on the supply side of the service equipment. When leaving the service equipment with branch circuits and feeders, you must isolate current carrying "grounded conductors" from non current carrying "equipment grounding conductors". Exactly the same thing you do if the grounded conductor happens to be a neutral conductor.
A grounded conductor can pass through circuit breakers and switches if they simultaneously open all conductors of the circuit, but a grounded conductor can not pass through a fuse as it is capable of opening while the rest of the circuit conductors remain in the circuit. This rule is not limited to grounded phase installations, but may be a little more common to see it done in those installations.