First of all, I did look for this issue before, this one is different from the ones I researched.
If you take a Ruined Long Range Scope and try to place it into an empty slot on the Mosin, it does NOT work.
However, if you have a PU Scope attached already and simply replace it with the LR, it works and the scope itself appears to be in a pristine condition upon use. The text however still says ruined.
As of this posting with the latest Stable build, this is confirmed to be working 100%