[vladimir998]

‘cause our electricity comes from ice cream trucks don’t you know. . .

[jimtorr]

Right, power comes from ice cream trucks. Doesn’t everyone know that?

Only at the end of the story do we learn that the tree also took out power lines.

[Songcraft]

They most likely sell that flavor from the "Dead & Buried" ice cream company called "Cow Power", which probably provided the electric power for the city, till that tree fell on the truck.

       

(Sorry about the reference to the commie "Dead & Buried" ice cream company.)

[rey]

Maybe it is radioactive ice cream:
http://www.frontpagemag.com/point/259857/ben-jerrys-has-new-radioactive-iranian-ice-cream-daniel-greenfield