Keeping and maintaining something that works is often safer than buying something new. Those kinds of helicopters haven't changed in a long time, and chances are, if they bought new, they would probably buy the same thing since the problem is getting parts to maintain it, not the base airframe.

Why waste good helicopter parts? I would have to think that the materials used in military applications are more robust than commercial. Refurbishing old parts isn't bad so long as it's done safely. The article says that the helicopter parts are inspected visually every 25hrs, a tear down is done every 125hrs, and any anomalous issue gets them grounded. No mention of problems with the refurbished copters.

Honestly, I think this is a very smart and efficient move on the part of the state. Reuse when possible, so long as it doesn't jeopardize safety.