To esy: I have applied for Dortmund, it looks like all people who applies for a German base are requested to attend the assessment session in Berlin.
I was invited there and there was mainly German people as it looks like they reserve Berlin for foreign applicants (not English) or at least for those who didn't ask to be based in UK. My assessment session was in fact an "open day" for everybody who wanted to interact with easyJet in any way
Cheers