The state laws only apply to roads and state bike paths. All other access is left up to towns and cities to decide. State parks here haven't said either way yet. They are legal on bike paths in some places and generally ignored everywhere. As far as I know, there isn't any legal place to ride them on mtb trails in the state. People are of course and shops are selling them, so we'll see what happens.
As you saw in the link, there is no definition other than 750w and 20 mph, so a Spedelc would not be legal because of the higher speed limit.