There is a 133 page handbook for implementing ANSI/ESD S20.02; it is ESD TR20.20. Here’s what it says about equipotential grounding and field service kits. Included in section 5.1.3:
“When neither AC equipment or auxiliary grounds are available, an equipotential bonding system may need to be used. In this situation, all of the items in the system are bonded together so that the charge that resides on the elements will be shared equally and therefore there will be no potential difference between the items. Once this step has been completed it is safe to handle ESD sensitive parts without inducing damage. A real life example of this is often observed in office equipment field service operations. For safety reasons the service technician will often disconnect the AC power cord which detaches the equipment from ground. In order to safely install ESD sensitive products into the equipment, it is necessary to electrically connect or bond together the service technician, the equipment frame and the ESD sensitive product. Once bonded together an ESD event will NOT occur when the technician handles the product or installs it in the office equipment.”