I drink city water, city has lead pipe, how is this safe? 6 years ago, I needed to replace the main water shut off valve to my house.  This required the city to turn off the water at the street. Incompetent city employee drives key through water pipe. Plumbers fix pipe, I realize that pipe is lead.  

Yearly, the city (90% of which was built before 1950) sends out a water quality report, which reports undetectable amounts of lead.  That is interesting since probably 90% of the city has lead pipe.

Several questions : 


How is lead pipe safe from leaching lead into water?
Do cities usually treat the water to prevent lead from leaching into the water?
What is the form of harmful lead (e.g. is it in aqueous solution, lead oxide, or forming  ligands with some other molecule)?
In light of the recent events in Flint Michigan, this issue has come to the forefront (see this article from the American Chemical Society's Chemical  &amp; Engineering News and see this article). To summarize:

Active Measures to prevent lead corrosion:


Maintain high pH. This makes lead carbonates less soluble in water.
Add orthophosphates which create relatively insoluble layer on the inside of the pipes.


Without these treatments, the addition of chloride disinfectants aggravates the corrosion problem by forming lead (II) chlorides (which is water soluble).

As mentioned by Jaroslav, the time that water sits in the system also plays a factor.