we don't happen to read it the same way.
I see that premises is not wiring that is "internal to motor control centers.....etc"
To me you leave that motor control center, say to a pushbutton on the othed side of the building, that is premises wiring (again, to me). In order to reduce a possibilty of potential from that wiring to building steel I would think we would want a electrode system
Well, first of all, if the pushbutton is on the other side of the building then it's not a part of the machine or it's control panel. It has to be local or it must be a part of a separate system that might be talking to the original machine. The local cabling from the control panel to the local machine are not premises wiring.
As to the requirement for bonding see:
NFPA79: 2007: Chapter 8 Grounding
NFPA79: 2007: Table 8.2.2.3 Minimum Size of Equipment Grounding Conductors and Bonding Jumpers
Typically at an industrial site the building steel is the ground mat. Properly done the steel is tested for continuity and ground. Three phase is brought from the facility and the protective ground is brought from the building steel. For an industrial machine the protective bonding is mandatory. Just not at the size of 250.30 . Rather it is a sensible sized connection based on the above referenced table.
Based on the "Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of the Equipment (Not Exceeding Amperes)"; 50A requires a minimum 10AWG Copper Conductor Size. ...but shall not be required to be larger than the circuit conductors supplying the equipment.