I found it when it was halfway out and watched the entire process of it pulling itself free and pumping its green blood into its wings to expand them. It looked like an exhausting ordeal and the Cicada paused several times (I presume to rest).
I would like to think it is now up in the tree-tops singing its summery song!
Here are images of the sequence of events. If you click on the first image, it will enlarge and the series will be presented as a strip at the bottom of the screen that you can then navigate through.