... and less than 10 years once you use the correct numbers. And that's assuming operating costs are 60% before debt service, which is highish.
https://www.cga.ct.gov/2012/rpt/2012-R-0515.htm
At 4% interest, 83 000 subscribers and attributing none of the costs of the fiber network to the smart meter project the payback period is 10 years and 7 months. A far attribution of costs to the smart meter project would bring the payback period to under 10 years.