A thought occurs to me just now: Why not also use that 40-60% waste heat to drive district cooling during the hot season? There's the absorption refrigeration cycle[1], which requires only a a heat input to drive the cycle to pump heat from the cold side to the hot side. Is the difference between the coefficient of performance between the more common vapor-compression cycle and the absorption cycle such that it is more cost effective to use the generated electricity to pump heat out of conditioned spaces during the hot season?

1. https://en.wikipedia.org/wiki/Absorption_refrigerator

Both cycles are limited by the same fundamental value (the Carnot coefficient) so I don't think that it would be a huge difference between the two cycles. Rather, I suspect that there are not all that municipalities that have (or need) both district heating AND district cooling. I expect that in the future we'll see a lot more industrial use of waste heat from power plants though, and part of that might take the form of on-site absorption chillers.

Combined cycle power plants do use the waste heat:

https://en.wikipedia.org/wiki/Combined_cycle_power_plant