my autocart system is a proof of operation that launchers and boosters still work just fine. as long as we have self resetting boosters along each track direction there will never be a worry and the subway should run at maximum speed.
unfortunately it cannot be automatic. my system has also shown that stationary carts in the holding tank get popped out to the side when the chunk is loaded up by a person being nearby. if the sytem is set in motion properly while loaded.. it continues to run, it's when people get too far from it and it unloads serverside then reloads that it fails.
solution. public chests or dispensers with carts in them, you get on the cart in the direction you want to go, you run down a small ramp into a booster/launcher which sends you on your way at max speed. when you reach your destination, you hit a wall (no dmg) and then destroy the cart and place in the chest there. or always carry your own cart to use the subway, the launchers and boosters should work fine despite the chunk loading/unloading.. we hope. I've come back to find my launcher running backwards, not sure if someone was inspecting it and fuct it or if it was natural loading bug crap as usual.