Freightliner is the manufacturer of the truck (a subsidiary of Daimler). They can read out lots of counters, etc, yes.
> should be able to do some back-of-the-envelope math and estimate
Even 200,000 miles of frequent stops in delivery usage is a heck of a lot. If typical EOL is 350,000 miles, you expect that there will be some trucks with a bit lower mileage. To think you're buying one of the lower mileage ones but get a 400,000+ mile truck is unfortunate.