One mating pair of sparrows have returned to my street! This after they declined to zero around 1976. May they prosper and thrive!
The best possible result we could expect from buses switching to LPG is the return of the bird population to former dead areas.
There must be other reasons though I can't think of any - even though dog numbers are severely declining, the cat populations have exploded (though they're now stabilizing as well), as have the rat, kite and crow populations. Those are rising still, so it's not like there are fewer predators around.
But I've seen similar brave sparrows all over Vasanthnagar, leaving the residential areas and edging on to the main roads. It must be the improvement in the air quality that's reversed the decline.