A lot of developers who have worked on ExtremeProgramming projects or strongly believe in XP principles end up finding themselves on projects where the customer or other team members don't really want to do XP. The developers find themselves doing a lot of XP things without really "telling" the others.
Some things that you can always do (and nobody really needs to know):
You can often get the customer to do a ReleasePlanning by just asking them to prioritize things. But without both sides committing to it, they can at any time appear with a different (the "official") release plan, or something else that renders your planning useless.