I live just a few miles away from this one. The last I knew the county did still own the road off of Greensboro Pike and was maintaining it as a utilities right-of-way. I do know that the gentleman living on the corner has been known to cause trouble for people accessing the bridge.
Ownership varies from state to state. I know in Kansas it is common for "abandoned" roads to be turned back to private ownership. In Michigan it can be either way. Fully abandoned and privatized roads do exist in Michigan, but many very long abandoned bridges and roads remain public and in these cases sometimes the property owners wrongfully claim ownership when they have no right to do so. The easiest way to avoid problems is to reach the bridge without being seen or heard. Not always possible, but I always try to stealth my way to abandoned bridges whenever I can.
Ordinarily, with an abandoned bridge, check to see if the corresponding road has also been abandoned first - because if so, then someone could indeed have snapped up what used to be the road and it would indeed be private property. I'm guessing you tried going in from the north off Greensboro Pike? That spot definitely looks the part of 225W being abandoned (per StreetView), as well as someone trying to re-purpose it into their private property entrance wouldn't be too surprising.
That said, these grounds being private wouldn't explain John Key being able to make multiple trips to get pictures of it, as recently as November 2018.
Went to check out the bridge and while we were there someone called the cops and we got pulled over after we were leaving. The cop did tell us it was private property, but isn't a county road? Anyways we got away with a warning, maybe because he couldn't actually charge us with anything.
Mike... You should have hollered being as you were in my neck of the woods! I haven't been over in a couple years, but the last I knew the gate was unlocked. The county still maintains right-of-way on that road as there are utilities down it. A man that lives by it supposedly claims he owns it, but doesn't!
There has been some interest in possibly making this bridge and road into a trail extension. I too would like to see it restored.
I am so in to monkey jack bridge. it would be nice if you guys would restore it. Because it is was one of the coolest bridges ever. Or open up the lane and let people walk down there. hope you open it so people can see the coolenst in it like i do.
If there is a question in my mind about access I check the county GIS, usually associated with property assessment records. They have different interfaces but I've found they almost always show roads, sometimes as a separate parcel with "no owner information" (tax exempt) as, as in this case, a marked right of way.
The county still claims a RoW for 225th on their most current map. (The RoW data has a 2003 date, so worth a call to the county road dept to confirm). Pulling up the county map to show an adjacent owner has served me well in a couple of instances.