Master Jedi...
This may be a complete over-simplification or overly holistic approach, but I think if you ask the right questions, within the right context, "flavored" the right way for the audience, then you can get exactly what you need.
In the end, if the business unit has to provide all the answers you're looking-for, you'll never get what you need.
The trick is to lead the conversation with your questions, and allow the business unit to respond. Ask more questions if necessary for clarification.
This way, the business unit thinks they're in control since they're providing all the answers... but you (the Master Jedi) are actually leading the conversation with your questions.
