FFS, Trashman, you're a ****wit. ANYONE who says that ships cannot and DO NOT jump while disabled, can fall into the group with him.
Calm down Hippo. Whether you agree with him or not it's no reason to start insulting him. If the thread does degenerate into a flamewar I'll have to lock it and I won't be able to rub Trashman's nose in the fact I've proved him wrong.
Secondly I'm going to say that I haven't made my mind up on this one yet. There does appear to be evidence for both sides of the argument.
1) There are three methods for a ship to leave the game.
a) A ship can have a departure cue set. This method will work regardless of the state of the ships engines.
b) A ship can be given ai-warp-out orders. This method will not work if the engines are dead
c) A player ship can press Alt-J. This method will not work if the engines are dead
This leans towards the conclusion that

intended for engines to be needed for a jump. Seeing as how the departure cue is used for things other than simple arrivals and departures from subspace there is a good reason for leaving it that way. There's no sensible reason for putting those limitations on the other two methods (especially considering that the break and never-warp SEXPs exist) unless the

coders wanted to make sure that disabled ships couldn't jump out.
2) The Colossus is given orders to jump out even though it is disabled. I don't think you can read too much into that though. The Colossus was only disabled at a late date in the mission's development. It's quite possible that this was an oversight.
3) There are several occassions where you are told to disable the engines of ships in order to prevent them escaping. Off the top of my head
a) You are told to disable the Iceni to prevent it escaping the first time you encounter it.
b) You are told to disable the Shivan transports carrying Bosch in order to affect his capture.
4) In the mission with the Tantalus the ship jumps out whether or not the engines are disabled. But if a ship can jump out without engines why doesn't it jump out regardless of whether the conditions required for the mission goal are met or not. The same thing applies to pretty much any capture mission in fact.
Based on the above I tend to lean towards the argument that jumps do require the jump engines to be working.