This morning while walking in Ladd's Addition, we noticed one of these "meta" art pieces screwed onto a utility pole in Ladd's Circle. These things are all over the area, as chronicled at Signs of Life PDX and other places. What it is basically is a photo of a utility pole (and the surrounding area that's been mounted on some sturdy wood and then screwed permanently into the pole that it depicts.
Check out the detail, these things are put up there with torx screws. That's not going to be easy to take off.