Good question, thanks for posting.
I had the same question on Monday when I saw one of our own aircraft hiding from the dust in the hangar with a similar improvised cover next to a sister ship with the red CFM56 covers.
As for you kevlarcarl, you must surely have more than a passing interest in aircraft to be even in this forum so to berate spotters is a little small minded.
Sorry to drift a bit but its a shame that there are more and more people that apparently don't give two monkeys about aircraft filling spaces in the aviation industry.