This feels like kinda of a useless comparison if we don't know about the tax rates they pay, cost of capital, adjusting for geographic location and local regulations etc. I.e. the largest increase was seen in NY where it is really expensive to do anything and high taxes.
Yup, tax exceptions, cheaper financing or even government financing. It's like letting the referees play the game and then pointing out that they make more free throws.
Based on the chart it seems than Maine was by far the highest.
Not to mention quality of service. Sure, electricity is electricity. Water is water.
But outages, outage response times, infrastructure, investments, etc. are the other side if the equation.
I have no idea. Maybe investor-owned utilities also provide worse service. However, without accounting for that, the article's claims don't mean much.