When the "Gadol Ha’ir" (literally, "leader of the city"), or community Rabbi, prepares his Erub Tabshilin before Yom Tob, he has in mind not only himself and his family, but also his entire community. They are all covered by his Erub Tabshilin, and thus if somebody forgot to prepare an Erub Tabshilin or was unable to do so, or if somebody’s Erub Tabshilin was lost or eaten before Friday afternoon, he is nevertheless covered by the Rabbi’s Erub. As such, he may prepare on Yom Tob for Shabbat. The Rabbi’s Erub Tabshilin is also effective for widows who are not accustomed to preparing their own Erub.
However, in order for this to work, all members of the community have to have a share in the Rabbi’s Erub. The Rabbi’s Erub covers them not simply by his thinking or even saying so, but rather by their receiving a share in his Erub. The way this is the done is by the Rabbi bringing his Erub to somebody, such as a neighbor, after reciting the Beracha and making the "Behaden" declaration. He then has that person take hold of the Erub with the intention of thereby granting a share to all members of the community. This is effective in granting the congregation a share in the Erub despite their being unaware of it, because of the Halachic principle of "Zachin Le’Adam She’lo Be’fanav," which means that a person can legally receive something beneficial for him even without his knowledge. Once they all have a share in the Erub, they are covered by it, even though the Erub consists of only a piece of bread and an egg, as even a very small share suffices for community members to be covered by the Erub.
There is some discussion among the Halachic authorities as to whether the Rabbi can have his wife take the Erub from him on behalf of the community. Hacham Bension Abba Shaul (Israel, 1923-1998) rules that a Rabbi should not have his wife take the Erub on behalf of the congregation, and he should instead ask a neighbor or somebody else.
It must be emphasized that one is not covered by his Rabbi’s Erub Tabshilin if the Rabbi does not follow this procedure. If a Rabbi is not aware of the need to formally grant his congregation members a share in his Erub, his intention to include them does not suffice, and his Erub does not cover those who forget or are unable to prepare their own Erub.
Summary: The Erub Tabshilin prepared by a congregational Rabbi covers congregants who forget or are unable to prepare their own Erub, but only if the Rabbi makes a point of legally granting them a share in his Erub, which he does by having a neighbor or other person take hold of the Erub on behalf of the membership.
