I know it is classified as one at DL, not sure about WDW. I could see them claiming it as an attraction, but I classify it more as a form of transportation. :shrug:
I think the NTSB categorized the WDW Monorail System as a private transportation system in their accident report from the 2009 accident. They based this on a couple things, but I think the most important thing was that you can ride it without the need for a theme park ticket. So, that classification may be enough for Disney to skirt the agreement with Universal...but keeping the Avengorail on the MK lines helps avoid an unneccesary argument.