The posts says two engineers are needed to work on Siri, and one reads literally: "We are looking for an engineer to join the team that implements the UI for Siri. You will primarily be responsible for implementing the conversation view and its many different actions. This includes defining a system that enables a dialog to appear intuitive, a task that involves many subtle UI behaviors in a dynamic, complex system. You will have several clients of your code, so the ability to formulate and support a clear API is needed."
The other one is for internal use with other Apple teams and aims “to enable access to their data and behaviors, and wire them up to your implementations. As a result, strong API design is needed to keep communications ideal.”
Seemingly Apple has much grander plans for Siri and it should, as we can imagine numerous scenarios in which iOS apps can take advantage of intuitive voice recognition and control.