In simple terms the sensor is triggered via a laser that counts sprockets and the light source flashes in synch with the sensor basically. The length of the flash is adjustable, as is the LUT used depending on the density of the film.
The film transport is sprocketless and the film tension is adjustable in real time via software. Anyway, I don't want to derail the thread further, but that it the overview of how it works.
As the links from Mike show, IB prints can transfer beautifully as long as you know what you are doing.
Check out the Battle of Britain DVD if you want to see how an IB transfer looks.