Municipal water reports usually tell the homebrewer nothing in the way of useful information. The levels that they show have to do with the safety of the drinking water, but not the ion concentrations that we are interested in.
Contact Ward Labs
and spend the $16.50 for the W-6 Household Mineral Test, or the W-5 test for $10 more if you have concerns about iron and fluoride. This will tell you everything that you need to know about what's in your water.
As far as the multiple municipal water sources are concerned, what I did, knowing that my municipality draws from 3 different sources throughout the year, was to send 4 quarterly samples to Ward Labs to see if there was any appreciable difference depending on the time of year and the source they were drawing from. There was virtually no difference in the 4 samples, so I'm fairly confident with the numbers that I have now. I still send one sample a year to Ward just for piece of mind.