I'm confused. In your first post, you said that it just started ticking after you picked it up, but now you are saying it was ticking before the warranty ran out? Was this oil change a long time ago? If you brought this complaint up before your warranty had expired, and can easily prove it (ie you have a service receipt even if it shows no problem found) then I would think BMW will step up to the plate and fix it. Give BMW NA a call with all of the details - when it started, when your warranty expired, when you told the dealer, etc.
Your dealer is doing the right thing though - they can't fix an out of warranty car without the rep's approval. If the rep denied it after the fact, who would pay for it?