The type would be a three phase panelboard. If you are carrying the wye neutral into the service, then it would be a three phase four wire distribution panelboard. Regardless of the style used, it would have to have a minimum 400 amp bus.

phase b

Yes, many parts of the US use 13.2 kV in primary line distribution systems. That is phase to phase. Phase to ground is 7620 V.

All high-voltage distribution systems are three-phase. Single-phase 'spurs' off the main line, supplying, for example, farm houses, are simply two lines of a three-phase system.

Any where that a three phase supply distribution is needed to operate three phase equipment.