Triple:
Look at the size of the structure you are in. IF it's a 900k Sq Ft whse & you have four xfrs each serving a 25% share of the space, then the grounding & bonding should be in that 25% area, provided that steel & water piping exist within that space.
The Twp I work in has structures up to 1.5 mil. sq ft and I have never ran into this debate before.
Think about a structure with 1 POCO service, split into 4 areas, each with a SDS xfr, all spaces have steel & metalic water lines. The grounding is done within each space. From a safety point, this assures that the steel & water are in fact grounded & bonded in the area served
