The article suggests that the act of replacing the cables could cause a catastrophic failure. My interpretation of this is that unless one could replace all the cables at exactly the same time (which is impossible), at least one more would fail, which would almost certainly cause the instrument pod to fall, destroying the dish and damaging buildings with flying cables.

judging by other comments, the observatory is obsolete. I believe they regularly paint the cables on the GG bridge in order to protect from corrosion.