I’ve ridden parts of it this summer. Here’s an older thread with a bit of info: Jimmys Round Top
Two weeks ago I rode through from the direction of Jimmy’s Round top again. (See here on Strava: app.strava.com/activities/187979415 ) The ATV trail improvements (yeah, I agree that it’s less interesting for riding) were within about 1 km of the Nine Mile River bridge. Equipment was still on the trail so they have probably made it to the bridge by now. On the plus side I managed to keep my feet dry!