Called BA Exec Club today. In a rather pleasant conversation my issues have been resolved. Here's a brief summary for the benefit of any other card holder in Germany:

BarclayCard Germany notifies British Airways by e-mail when the annual spend surpasses 20,000 Euros. BA tracks this information in an Excel sheet. There's no information sent out by BarclayCard to the customer and the 241 isn't visible on the BA web site. Bookings can only be made on the phone. You need to call BA to find out if the voucher has been issued. The plan is to automate this process someday, but it appears that IT is a bit slow on this project.