I was told that, on old lead pipes, the surface oxidises and massively reduces the amount of lead in the water. Not sure how true this is.
We recently replaced the lead water main in our place while doing other works. The water company paid for all work outside the boundary of the property, while we paid for all works inside the boundary (excavation, connection of new pipe). We just had to make sure that the plumber was on-site when the water company turned up to swap the supply. They also inspected the excavation and positioning of the new pipe to make sure it complied with regulations).