Ba humbug. Here's my answer to this issue. The key Business / IT engagement question is:
What are some of the biggest issues or opportunities that need to be addressed for some of your core customers in the relatively near future?
Let's not try to answer this question holistically - stay with some of the more important things we should try to find solutions for over the next few months. Also, watch for the red herrings - cost concerns, organizational needs (most common: getting more people into the discussion), resource contentions, etc.
I'm not saying product strategy isn't important - it is very much so. I'm also not saying that you should avoid dealing with issues of cost, people, process, and change - you must. However, I'm specifically saying that none of these should prevent having the dialogue on short and medium term priorities.
With these questions answered - and even if there isn't complete alignment on priorities or vision - a technical team can start mapping out solutions. They will focus on the items that have the highest priority and cleanly articulated vision. They may also suggest some technology oriented activities either to prove out a technical approach (R&D) or address a specific operational issue (defect management or technical debt). They can then go back to the Business Managers and say, "Well, what if we delivered the following items over the next few weeks to start, followed by these other things afterward? We'll demo what we finished and we can reset priorities then based on what you see."
This is how agile planning and delivery starts - and the first steps to developing a healthier Business / IT relationship.