They chlorinate the lines, as I ran readings to see as to how many charcoal pre filters I need for my RO plant, to get the CL out. They can be overcome with cl and in a short while the cl will just run thru. The problem is breaks in the line, as ya see around town. Mostly the small household lines the people put in, from their house to the main line,,is a lot of the bad water problems in RP. They use thin wall plastic pvc pipes to save costs, or don't dig them deep enought to the main line for the city to connect. A break or leak will occur and when city water pressure is low, or when ya get no water, then the pressure builds up, it can suck germs and water up back into into the water line, to your house. Generally the city has good water from deep wells.
I just use a CL injection system to treat the ups and downs, and a CL filter to remove all the CL. And drink out of the tap.
So to get back to your question, yes they treat the water at RP! But, as landshark said, the little critters in the tanks are a good source of protein! You really don't think there not in some US water systems!
Basically if you have a CL tester, test at your sink, and it shows a residue of CL, you can drink the water. But, if ya don't check daily, something like a break or leak up line can cause the CL to be used all up, and that's when ya have or may have bad water.
So RP has good water (drinkable) at the start, but down line problems can cause harm to you. Generally it's ok to brush your teeth with the tap water.....as I also know many RV people who hook up to the water and use it for everything in the rv, drinking and cooking and so forth.
Sometimes when people get the poops, they may blaim the water, but may be the food eating out.
DD