I am not addressing the “kashrus” of the eruv eruv per se. This comment is addressing the following “I spoke to some of the people who are in charge of the eruv , they mentioned that they are aware of people carrying outside the eruv and they dont find it a problem. Therefore they must be relying on something else, not a backup eruv”.
Perhaps they are relying on the eruv and are not concerned for whatever reason that people carry outside its boundaries. I don’t know the answer to this question and am not trying to answer it, but, should the eruv be invalidated on the grounds that people carry outside its boundaries? Those who erected the eruv, are they hiding those boundaries and keeping them a secret purposely? Are they obligated to take down the eruv because some people are to lazy to find out what area it covers? These are not rhetorical questions. Perhaps these are questions asked of a posek and they received a reply that allows them to maintain the eruv despite those who carry outside its coverage area. Why assume the answer is “backup eruv”, because those who carry use that answer? Moreover, if you spoke to those who erected the eruv and you raised this concern, why didn’t you ask them what they rely on, instead of assume an answer on your own and be left with a question mark?