If the metal water pipe had not been bonded then there would not have been a complete path back to the transformer and the plumber would not have been hurt. This is a good case of why not to bond.
Remember there must be a complete path before current can flow.
The deaths in Iraq are due to the lack of earthing of generators and would in no way apply to this discussion. They are getting hurt due to NEV or neutral to earth voltages. This is mostly due to the difference in the way the different countries manufacture their equipment not due to a connection or the lack of a connection to a water pipe. Most of the water pipes installed on the bases in Iraq are nonmetallic.
Treated water such as water supplied from a utility will most definitely carry current. The more chlorine that is added to the water the better it conducts.