Note however that it is easier to limit and monitor air pollution generated by relatively few generation plants, than by hundreds of thousands of individual cars.

While the only 100% hydroelectric regions I know of are the pacific northwest USA and eastern Canada, I live in an area with 60% hydroelectric and nuclear. 30% is natural gas. The last 10% is a split between coal and renewables. So a battery electric vehicle is 65% near zero emissions, and 95% is less polluting than oil. (Without considering the inherent efficiency of battery powered motors vs. internal combustion engines. Or the environmental footprint of manufacturing "green" machines, building concrete containment domes for nuclear plants, nuclear waste disposal, or methane leaks).

Even pure displacement of air pollution to smokestacks is a huge plus in places like midtown Manhattan where the most respiratory health harms due to particulates, NOx, ozone, etc. are taking place. Less kids getting asthma, people getting heart attacks/strokes, premature births, etc.

Displacement results in better health outcomes, which is the whole point.

This is a false dichotomy. Certainly it is true that reducing air pollution is better than not, and certainly effective public transit reduces total air pollution both by being more efficient, and because power sources are never 100% fossil fuel powered.