The reason for a water supplier to call a boil order, usually has to do with the detection of coliform bacteria in the system, these bacteria are "indicators" of possible bacteriological contamination. For a drinking water provider, even 1 coliform on a test of finished (treated) water could be cause for a boil alert.
If you did a coliform test on your normal aquarium water, it would usually have a result of TNTC (too numerous to count) coliforms. I tested my normal tank water a number of times, when I worked as a chemist/microbiologist at a drinking water facility, my tank water was always off the charts, with coliforms.
The thing to worry about with your aquarium, is that due to that indicator being found in the distribution system, will mean the water provider may super chlorinate for the next couple weeks to purge the system of bacteria that could cause a water bourne disease in humans, and that extra chlorine is much more dangerous for your fish than few random coliforms. So if you do water changes, be sure to add enough dechlorinator to neutralize an eventual slug of highly chlorinated water flushing thru the system.