New Datapoint. Asked for AUP at BERlin last Wednesday. Unfortunately the check in lady (Economy or bag drop) didn't know and told me I have to call BA. As I refused and told here that's it's not possible to make an upgrade via telephone 65 minutes before departure and that a lot of people had it done before at the same place she became wet.
Luckily the check in lady for Priority check in came at this moment - but I think she were not interested to "help" me. So she said an upgrade might be between 180 EUR and 250 EUR.

At LHR asked for an AUP to EZE, but no availability for J.