>The goal of electronic trainline brake activation is to have the entire train set up almost simultaneously to avoid slack and make the train more quickly respond.

This has been the goal of air brakes since the 1880s and has worked quite well until the efficiency sexperts got ahold of things in the 1990s. In one form or another, these electric/electronic brake systems were tried in the 1890s, 1910s, and 1930s and given up on each time (except for captive fleets like elevateds, subways, and commuter operations) because the cost of installation and maintenance expense always produced a significant negative return on investment. On other words, the regular air brake systems had become so good, they weren't worth it. There is a threshold between reality and never-never land, and these fuel miser maniacs have crossed it.