The city of Copenhagen cleans up once in a while. Bikes are taped like this and if the tape is unbroken after a certain period of time, the bikes are removed.
They'll be sold later at an auction.
As far as I recall they put ads in the papers and put up posters to inform you of the removal date. You snooze, you lose.
Even at my flat we have to clean up old bikes. We have a traditional Danish cooperative-style system - similar to a strata council i believe - where we own shares in the building and own our flat. There are maybe 40 flats and we still have to get rid of old bikes once a year from the bike sheds.