No, haven't figured it out since. The car has been in the dealer not once, but twice; they replaced all belts, pulleys and vibration damper, and the sound returned.
I'm kind of used to it now, although sometimes you cannot hear it at all (also, if you rev the engine just a bit before locking the steering it will not do the noise), it's still annoying when you do.
I saw a video online when someone applied some soap to the outer edges of the belt to cure a squeal. I will try to do that and see what happens, but it's too cold now to work on the car.
BMW 320 dA LCI, BMW PPK - 197HP, 2010, sapphire black, steptronic