I don’t know much about art…., originally uploaded by spinneyhead.
Clearly, this is an indictment of the wasteful nature of modern consumerism. The juxtaposition of the shopping trolley- a widely understood icon of consumerism- with the waste bin is obviously telling the viewer that most of what they buy ends up on the refuse pile. Putting the rubbish straight into the trolley simply and symbolically cuts the shopper out of the process.
Alternately, some Scallies thought it would be a laugh to vary their vandalism.