I did a quick google search for Magruder Road in Midland County and I found a map that shows it. It is a 2005 county map showing road construction projects, but based on what I see, Magruder is a fairly long and prominent road. So, unless there is a section of it that turns into a seasonal road, it would seem to me that it is a standard road (even if dirt) that could be traveled by a regular licensed SOS vehicle. I obviously have no idea exactly where this is or what the conditions are, or anything else, but just the fact that I found it quite easily on a map seems to me that it's somewhat of a "real road". Shrug.
Here is the map I found online. Magruder runs north-south across M-20. It breaks a couple times and continues near the north county line.