Abby from Google quietly announced in the Google Maps Help forum that those who share photos publicly and have location data on the photos within Google+ may find their photos automatically within Google Views and Photo Sphere.
Abby wrote:
Starting this week, photos with locations that have been shared publicly from your Google+ account will now appear in Views (g.co/views) in addition to your photo spheres. Some photos may also appear Google Maps, making the map more useful and comprehensive for everyone. You can also go to Views and directly upload or import new photos to expand your collection.Visit the Help Center to learn more about contributing and managing your photos on Views.
So if you find your Google+ photos in places you did not expect, this is why.
Forum discussion at Google Maps Help.
