It's not uncommon for towns without deep coffers of cash to convert 'retired' fire apparatus into public works trucks. ISO criteria call for a twenty year service life for first-in fire engines and trucks; after that they can be used as reserves, but generally speaking, reserve apparatus gets replaced by retiring first-line rigs before they are used up.
Consider that most fire apparatus is "over built" for reliability and dependability but doesn't accumulate much mileage while in service. That's why most apparatus gets surplussed out to smaller and smaller communities rather than being crushed.
There's even a long tradition of many fire agencies "refurbishing" older apparatus into more modern rigs . . . still retaining the original low-mileage chassis but upgrading pumps and equipment to new standards. "Refurbishing" usually includes a newer cab to meet newer ISO standards, etc., but it's still the same old chassis.
But many enterprising communities recognize the value of that low-mileage chassis and cab, and have been known to convert the "old" firetruck into a street department workhorse or water department rig, etc., extending the life of their investment and maximizing their return-on-investment.
So, yes, you'll see a lot of 'retired' fire apparatus converted to dump trucks and flatbeds and welders and all nature of haulers.
The one Chuck found looks to be a nicely restored rig in private hands.