I don't think we have been told this was an ungrounded system, only that they did not extend a neutral conductor.
Back in the glass house computer room days they never extended the neutral beyond the service disconnect or secondary of the transformer and these were usually wye systems. The only time you really need to extend the grounded conductor is in a corner delta and that is because it is one of the phases, albeit a "white" one. The others can stop at the main bonding jumper.
