Its not a free for all, but there are some legacy pipes with lead in them. The EPA currently limits the amount of lead measured in drinking water lines. This is where the root of the problem happened in Flint. They had lead pipes that had calcified and were not delivering contaminated water. They changed water sources which changed the chemistry of the water causing the lead to corrode into the water.

Yes. They were installed many decades ago and haven't been replaced because a) it would be extremely expensive to do so and b) there are additives which AIUI prevent or at least significantly reduce leaching.

I'd be shocked if the EPA's cost estimates turns out to even be within an order of magnitude off the actual cost. Maybe they're just measuring the cost to utilities for the parts not on private property.