Does oxidized copper conduct electricity?
The oxides are non-conductive as they have a full valence bands, but if you "dig into" the wire, you'll get to metal that isn't covered with an oxide. CuO is pink, but does not complete the valence rings, so you get Cu2O after a time, which is black.  The green is either from a sulfate or carbonate.  You have CO floating near the engine, you'll have some green after the Cu2O reduces.  If you see green near the battery, it's because the sulfur from the the battery has electromigrated up to the connector and gone it a lower energy state there.  You see this when you have a "bad cell".   I'm pretty sure it's Cu4SO4 with some (OH) hydrated state. 

Anyway, you need to take some steelwool and clean off wires in order to remove the oxide if you want to remount them.  You could put them in a glass of Coke and have the phosphate reduce the copper oxides.  Everything just wants to be at a lower energy level, and if you are there, you don't conduct.