Commercial Generator and ATSs.

[hillbilly1]

For Normal Power, yes all are supplied At the service.
Yet...There are 3 separate - 4000A, 480V service disconnects from 3 separate utility transformers in the Utility transformer vault. Each service is separated from the other service disconnects. They all share the same premises building ground from cold water and structural steel, tied into a large copper ground detail, oversized conductors as per specifications from EOR.

Those can be all common as long as the neutral bonds are BEFORE the ground fault sensors, egc also shall be before the gfs. On the three pole switches, the egc should be connected before the ground fault switch, no neutral bond at the transferswitch. The four pole switches maintain the bond depending on utility or generator position. When on utility, the bond is on that side, when on generator, the bond is routed through it. Both are bonded at the same point ahead of the gfs on either end, it just keeps the bonding from making a loop and an alternate path. The alternate path will cause nuisance tripping, and even possibly negating the ground fault protection.