That loco's modern replacement is for commuter service within Los Angeles where everything possible is being done to reduce air pollution. Retiring and destroying the 30 year old non-conforming diesels was probably a condition to qualify for federal and state participation in the cost of a modern replacement locomotive.
Commuter rail is subsidized there to try to reduce the number of automobiles on the road. For two reasons: 1) reduce exhaust smog, 2) subsidizing rail is a lot cheaper than buying homes and business alongside existing freeway corridors to widen and increase the carrying capacity of existing routes. Los Angeles traffic is world-famous, anything that gets some people to commute by rail helps reduce traffic congestion.
30 years ago my comment on LA traffic: "They have a strange custom down there. 5pm everybody goes and parks on the freeway for a half hour. Some might crawl along a few feet. Then at 5:30 they start moving again and everybody goes home". Anything to alleviate that, is progress.
