Ecco cosa dice in un articolo di supporto Apple :
iPhoto — and Aperture, if you downloaded it — remains on your system in the Applications folder, and you can continue to use it. If you open iPhoto or Aperture after you upgrade to Photos, you’ll be asked if you want to open your library there or in Photos.
Any changes or edits you make in iPhoto or Aperture aren't reflected in Photos. And any changes or edits you make in Photos will not be reflected in iPhoto or Aperture.
Sembra che tu sia in grado di aprire le foto in entrambe le applicazioni, tuttavia le modifiche non verranno sincronizzate tra Aperture e Foto.