It probably makes most sense in urban areas where a totally full truck can leave the local depot and fully unload in less than 15 miles. That's the case with my local UPS (in the greater NYC area). Electric vehicles are perfect for this scenario.

(This said I'm sure they'll have to have contingency plans for when the things run out of juice but that's probably the same plan they currently have for accidents or breakdowns)

Which EV did you buy? I have a 2015 Tesla S 70D and the weather, heater, etc., don't seem to make as much difference as you say. But it is the only EV that I have any first hand knowledge of.

Mind you, the real range is nearer 200 miles so I rarely need to worry about running out. On a 10 A, 230 V, single phase connection (Norway) it will add more than 80 miles overnight (say 18:00 to 06:00) so it is perfectly practical for everyday use.

At a Tesla Supercharger it takes an hour to go from 20% to 80%, that is adding over 100 miles.

Tesla seems to be the only company nowadays invested in developing an actually good electric vehicles I never understood why the other car companies insist in producing crappy EV products and yet so expensive for what they are worth.

I wouldn't recommend buying an EV that is not Tesla.

What's wrong with Nissan Leaf or Hyundai Ioniq?

A UPS truck probably wouldn't need to turn on the interior heater -- those trucks usually have an open cab anyway, and the driver spends so much of their time outside the vehicle that it's probably not worth the effort.

I wonder if their estimates are taking into account the type of work the truck will be doing.