I don't think iPhoto uses NSCollectionView... NSCollectionView is new to Leopard and iPhoto's had its photo viewer for much longer.
However, they work similarly, in that they display a sort of grid view. You provide NSCollectionView a prototype view, and when you hook up appropriate bindings, it will manage copies of that prototype view for each represented object in its content array and display them in the grid. It will also do some automatic animations for you as you add/remove/rearrange items.
There's some good examples of how to use it on developer.apple.com. Look for "IconCollection" and "SourceView"