Two webpages on the topic. The first is the article, the second is a photo-slide.
http://detnews.com/article/20110919/...with-neighbors
and
http://multimedia.detnews.com/pix/ph...y/091811spire/

I think those people should have been dispersed by the police.
They do not own the property.
I could imagine them questioning the common sense of dispersing them if they were actually boarding up windows, cutting grass, landscaping, and repainting the house.
The building is 'abandoned', meaning the owner does not reside there, but trust me all property has an owner. Perhaps they should buy the property and spend rennovate or demolish it.

Here is some questions:
Who is going to maintain this 'art installation'?
What will it look like after the first snow?
Will the materials get loose and become common wind-blown trash?

Detroit needs people to purchase and rennovate homes, thus reducing blight, creating economic density, and inspiring neighborhoods.
If that is not possible, at least board up and secure empty propertys, perhaps without permission.
But please, don't divert the little good will the city gets from outsiders to erecting tire heaps.