for those unaware, the eruv is a piece of wire stretched between lampposts of much of NYC at the behest of the Orthodox Jewish communities; it forms a loop enclosing many square miles of city blocks, and is used to "extend the private domain" to circumvent shabbat restrictions
for those that follow a strict interpretation of the Torah's teachings, Shabbat, or the Sabbath, is a pretty important part of the practice; on this day, a Jew may not "do work", which includes many activities, such as lighting fires, which, in modern times, includes electricity.