With regard to the ” Brain Train”, the idea is an interesting one, connecting UGA, Emory and Georgia State/Georgia Tech via the current CSX route. Unfortunately it will not occur because of two major obstacles: 1. CSX won’t give right of way to passenger trains and 2. The unwillingness of either the public or politicians to support the financial burden. In point of fact these obstacles exist throughout the USA and prevent comprehensive mass transit. Years of neglect to whatever mass transit systems we do have coupled with the obstacles mentioned make it highly unlikely that we will have any elaborated systems anywhere in the USA.
To appreciate what other countries have done and continue to do, view the excellent NOVA
https://www.pbs.org/video/london-super-tunnel-xlvcul/ on the new underground line in London. It shows the history and continued commitment to mass transit that is found elsewhere in contrast to the pathetic American approach.