On Zootierliste this species is called Ninox boobook -syn N. novaeseelandiae and mention 45 public collections in Europe keeping it. I know it is also kept in quite a number of privat collections.
Well presumably all the Boobook in Europe are of mainland Australian provenance, making them Ninox boobook (if you accept that 2013 split from the NZ/Tasmanian species, Ninox novaeseelandiae, which obviously Zootierliste do). This also means there are no morepork in Europe, as this name refers solely to the NZ species. But this (very detailed and much appreciated) sign either ignores this split, or (more likely) pre-dates it.