corporate-wage-slave

Well there is definitely a sign at the MUC check in desk, blue section at the bottom of the A4 sign, it's flat on the desk, and there's a sign on the MUC departure gate too, on the front side. Not giving the full letter on request is in breach of the regulation, however you look at it, but it won't get you far.

Irrops at airports are often poorly handled and it's difficult to come away from the experience with a positive impression. I doubt you could have done much more, and in the circumstances to get to NY within 2 hours or thereabouts was better than some other options.

You could try the EC261 route (BA may have set the MUC flight for payment anyway since I'm sure there would be many passengers who were delayed over the time limits), but on the facts it may need some arguing, and a statement from you about when the doors opened (and any other evidence you have). I don't have high hopes, there again I guess you have little to lose.

The alternative is to treat it purely as customer service remediation, and though you doubtless found it all annoying, it doesn't strike me as truly appalling experience. So I'm not overly confident that will get you more than a few Avios.