My guess is this is something they had to do. All newer monorail type vehicles out there are pretty much autonomous. So if they were to purchase new trains instead of retrofitting the current, they probably couldn't run with the new with the old in a transition period. With retrofitting the current trains, they can switch between the autonomous mode and legacy mode as they did during the implementation over the past few years. If they just purchased new autonomous trains they would probably have to completely shut things down for a lengthy amount of time while old trains are removed, new ones are added, equipment is installed/tested, etc. Now they have the framework in place for autonomous trains so should they be replaced down the road, it won't be as harsh of a transition. Just my opinion as an IT guy who specializes in integrations.