I had only limited experience of the BIAZA awards during my time in zoos but from what I recall the zoos have to nominate themselves for awards-they have to put together an application of some kind with details of the project and justifying why it should win. My experience was on the education/conservation side though and it was a while ago so it might be different for exhibits. If its the same still then I would guess it takes time to put the nomination together so maybe theres a delay time between an exhibit opening and being entered for an award?