Okay, so obviously there’s more than meets the eye here. Siri is using AssistantExtensions, a jailbreak tweak that allows you to input various bits of knowledge into her “brain”. Think Neo’s “I know kung fu” quote from the Matrix for an idea of what it’s like.
If you haven’t read our post on AssistantExtensions we urge you to do so. It, along with the Jailbreak FAQ Add-on can be downloaded for free from Cydia’s BigBoss repo.