Rabbi JD Bleich discusses it in Tradition 39:4 (2006).
In summary, and again, these are all theoreticals:
- If we are positive (?) that this person is a rodef, i.e. actively trying to kill innocent people, then we can use any force needed to stop him, including lethal force.
- Is torture worse than lethal force? This is debated by the Rishonim, but it appears the majority opinion is that if killing is allowed, torture is too.
- Suppose this fellow has knowledge of the ticking-bomb plot, but wasn't involved in setting the bomb (but if he disclosed his information we could stop the bomb); that's more complicated, but I think Rabbi Bleich concludes he's also considered a rodef.
- How sure do we have to be that he's a rodef? That's very unclear ...
- There are similar arguments involving kofin oso ad sheyomer rotzeh ani. It's complicated.
What if this person is entirely innocent, but it's necessary? E.g. evil terrorist won't talk no matter what we do to him, but if we torture his family he'll talk. You can't call the family a rodef.
When a significant portion of the world population is at risk, there can be a concept of emergency dispensations -- hora'at sha'ah -- that might allow more than otherwise would be. Rabbi Bleich said this might be analogous to a court-mandated "torture warrant" suggested by Alan Dershowitz.