This plastic bottle installation is part of an operation called “Paris Illuminates Paris”, which mixes the recycled green Sprite bottles and LED lights to create the Christmas lights down Rue Richelieu (near Palais Royal). This was the creation of Fabrice Peltier, a gallery designer, for 2009. I snapped this shot just last week so that answers my second question... Did they re-use the decorations? Yes, as you can see.

There are also four or five trees in Place André Malraux at the foot of Rue Richelieu. You can see a close-up of the construction below on the left.

Holly announced that she was going to be drinking a lot of Sprite this year to make her own! (The red ones are Badoit bottles.)

(Thank you, Peter (Peter's Paris) for pointing out these trees!)
Also, Anne featured this scene (in the daylight) at Just Another American in Paris here.