Me, i would ride it. BUT: in many states, by law motorized use REQUIRES owner's permission EVEN IF NOT POSTED for No Trespassing. Like I bet most suburban homes in your area aren't posted No Trespassing, but that doesn't mean you can go roosting around their house. And it prevents people who would tear down signs and then claim they didn't see any, from getting a free pass.
We may not like such laws and no harm, no foul, but it's not foolproof that there are no signs. The best way to find out if the road is PUBLIC is to check with the township. Like if it shows up on the tax maps (which are often available online; in my town in a different state they are) as a public road. "Private but tolerated" is case-by-case and requires "local knowledge".
In general while powerline riding is often practice and sometimes tolerated, it isn't actually legal. If you actually asked the power company they'd probably say "No".
Advanced pancreatic cancer found 04/2010. Have outlived +/- 97% of patients with this diagnosis, but 08/2013 cancer now in liver, vascular system and lungs with 20+ lung tumors. Sick/weak sometimes, not riding much. No more treatments & now under Hospice care.