Quick answer:- no.

We had a fast talking chap try to convince us that "investing" in replacement lighting would pay back in 6 months. Brilliant. Until you looked at his figures where he used the TOTAL building load and the percentage saving from the lights in the same calculation. We did change the lighting eventually, but payback will be several years. This council sounds like they have been bamboozled or they did it for other reasons, not cost. Maybe the grant helped......

p.s. the payback per year, does that come after maintenance costs have been allocated?

I've not checked and won't comment on any numbers in detail, and have no information other than skimming the news article, but it is worth noting that it is a car park canopy on the council's flagship building. It might therefore have added value from the amenity to council building users. The cost might, or might not, include car charging facilities. Given the front-of-house deployment it is possibly also a statement of intent from the council. It also therefore no doubt increases the value of the site, having a book value. There may be budget that "needs" spending (unlikely in the current clime) and there may be tax relief on capital expenditure (I am not an accountant). From a cold-hard-cash perspective these things might well aid staff retention. And energy costs are not coming down in the long run.

So while it might seem expensive as an investment, in crude numbers there is a 25%ish ROI over the design life, notwithstanding O&M as Roger G notes, and councils should be applauded for thinking long-term. Some of these wider benefits councils will rightly spend on with no expectation of a directly-linked return. I know my extension, which gives me a lot of amenity, definitely isn't generating me any money.

I would expect the same logic would also apply to another large business able to think long term about its assets.

I wouldn't expect a standard rooftop solar system to take so long to pay back; solar carports are not advertised as the cheapest solution as you get other benefits.