Basically do we have any examples of this sort of situation, where there was an imminent threat to life and people were saved due to torture?
Most evidence points the other direction.
> Finally, an exhaustive 2014 report by the Senate Select Committee on Intelligence analyzed millions of internal CIA documents related to the torture of terrorism suspects, concluding that “the CIA's use of its enhanced interrogation techniques was not an effective means of acquiring intelligence or gaining cooperation from detainees.” It adds that “multiple CIA detainees fabricated information, resulting in faulty intelligence.” https://www.scientificamerican.com/article/we-rsquo-ve-known...
https://www.intelligence.senate.gov/sites/default/files/publ...
In the made up scenario you could make a case that even if there is a low probability of torture working, the scale of lives saved would make it worth it. A 20% chance of saving 1M people is still net +200k lives.