It’s not quite open data in the classic sense of the term, but it’s a step closer. Under the hood is a WMS service, which you can think of as a way for web maps — their map, your map, my map — to request data about the trees of Charlottetown. So I can craft a request to, say, grab an image of the trees in Hillsborough Square that looks like this:
Which returns this image:
The WMS server, however, doesn’t appear to support returning anything other than images, as setting the FORMAT parameter to XML or JSON returns an error. So the WMS server is more like a picture of open data than open data itself.
But, like I said, it’s a step.