Not really apples to apples. Letting something set "for several years" will cause the grease to set up and harden.
I spent a bunch of time in the concrete business. All the tensioned cables are coated with plastic, because as you said, without it, brine on the road would rust the cables. Bridges are always the lowest spot in a road, therefore, brine accumulates there. Concrete is porous. If you fill a concrete vessel with water, it will slowly seep out. There are a host of older, smaller bridges that have re-rods in them. They are rusting out, but the politicians would rather spend money on parks & bike trails. You get more votes that way.
jerry