Hate to resurrect an old topic, but a full Special Delivery Prefab has been made available on Gamebanana for anyone who is still looking for the logic.
http://tf2.gamebanana.com/prefabs/6207
I'm looking at it right now and it appears to have everything intact, and even comes with a demo map so you can see how it works.
So it includes: The rocket with a blast pipe, like the one on doomsday
The rocket without a blast pipe
The Australium case with the smashed crate, same as in doomsday
The demo map so you can check how it works
Each of these come in separate vmfs that you can copy/paste the pieces from into your maps.
Also worth noting, it comes with all sound effects involved as well built in.