The Airprox summary report is available from:
http://tinyurl.com/5pmx7w (.pdf file, 668 Kb)
One aspect that I think was missing from the Airprox investigation is that it might have been something (Chinese lantern?) caught in the rotor wash - the lights were reported to have been orbiting the EC135.
Does anyone know the direction in which the blades on the EC135 rotate? if the orbital direction follows the sense of the blades, then this possible explanation becomes more likely.
Joe
Apologies, I just noticed the URL for the airprox was already included in the original post!