Bidders demand Thames Water granted immunity over environmental crimes

Well, depends on the municipality. My local government does water, and according to this, that's more-common than not, but that's not a universal.

https://en.wikipedia.org/wiki/Water_privatization_in_the_United_States

In the latter half of the 19th century, private water systems began to be a part of municipal services.[1] As of 2011, over three quarters of US local governments surveyed by the International City/County Management Association provide water distribution entirely with public employees. Over two thirds of municipalities provide water treatment publicly, and over half provide sewage collection and treatment publicly. These rates have remained relatively stable over time.[2]

Private water companies have been operating in the United States for over 200 years and now number in the thousands. Collectively, the private water industry serves more than 73 million Americans.

Is that not inevitable once this round of vultures pick at the carcass some more anyway?

That debt will be bigger the longer it is left before nationalising it. The situation shouldn't have been left to fester for so long.