That is right, the sleds are back! We said that they will be gone until we figured out what to do with them and so we have. So what did we do? Did we fix them? Did we made it impossible to get into bases with them? Did we remove the ability to turn into a submarine with them? No. In fact we decided to embrace the meme. They will go back exactly as they used be. We decided to make it the most powerful base building item in the game.
You will have to work for it though. For such legendary, fear inducing item cannot be obtained easily. There is only one place where you can find it. Inside the nuclear powerplants core. Yes highly dangerous but worth it, because the sleds will take you where ever you wish to go.