Take a close look at the neutral conductor in the seperate secondary wires that run from pole to pole. When the hot secondary conductors are broken so as not to connect two transformers together, the neutral will be kept continuous.
At each transformer, the secondary neutral will be bonded to the ground wire running down the pole to the butt plate (or ground ball or ground rod) as well as to the transformer can itself. The low side of the primary will be bonded to the inside of the can.
If there's cable TV and/or telephone on these poles, the support messengers for them will also be bonded to the same ground wire.
In my mind, I see the PoCo primary neutral interconnections as being similar to the way the NEC has us hook equipment grounds together out on branch circuits. . .if they are present at a location, they are all connected together. Kinda forms a web.