I have Aperture and mostly use it instead of iPhoto. However, it seems like I cannot use Aperture photos/videos in Premiere Elements. If there is a way to use Aperture photos as in iMovie where you can drag and drop Aperture photos and videos into the movie, please tell me.
I don't know what Aperture is, but if you go to the File/Import menu on the Elements Organizer on a Mac you will find the option to import your iPhoto library into the Organizer -- and then you will be able to move the photos into a Premiere Elements project from there. You can not interface directly between Premiere Elements and iPhoto or Aperture however.
You can also just use Premiere Elements' Get Media/From Files and Folders to get any photos or video into your video project.
Aperture is (or at least was) an Image processing program, rather like Adobe's Lightroom. It has a cataloging function, but offers Image processing capabilities also.
As for working with the resulting Images, if Saved to a common format, such as PNG, JPEG, GIF, PSD (do not recall if it can Save_As PSD, the Photoshop format?), etc., those Images should Import just fine.
As for the Aperture Catalogs/Albums, I do not know the answer.