[loup-vaillant]

Yes there are. So to an "outside observer" (like an omniscient being from outside our universe), it's definitely deterministic.

From the inside however, we still have the Born probabilities to contend with: apparently, our subjective probability to observe one version or another is tied to the square root of the relevant amplitudes. In the case of a half-sieved mirror, that's one chance in two. But we can easily bias this with a stronger (or weaker) mirror.