Is it Art?

Without explanation of intention perhaps not. Except, when encountering unexpected public art you might well not have an explanation as the artist wants to  leave you to engage with the work on its own terms. What might it be? A marker, a boundary post, a person? I was reminded of going to see a stage play in the Festival many years ago - Boris Gudunov - in which the main prop on an otherwise mostly empty stage was a massive plank of wood. It was used in all manner of ways, including upright as a tree, crashing to the stage to signify a death (I think) and laid flat between chairs when it provided a bouncing platform for galloping horsemen.