In 1998, when the Montreal-based collective ATSA declared a state of emergency and held its first edition of État d’Urgence (State of Emergency), a socially engaged and temporary public art project seeking to call attention to the state of homelessness in downtown Montreal and of citizens around the world forced to exile because of wars or political instability, it did not anticipate that this project would unfold over the course of two decades. However, the recurrent need to remind the authorities and the public of this persistent issue, as well as the positive impact that the project had, led the artists to hold an edition of this project almost every year. Since Pierre Allard and Annie Roy founded ATSA in 1997, one of the main aims of their public interventions has been to stage encounters between complete strangers or between groups of people that do not necessarily talk to one another, such as homeless people and city representatives. By focusing on two of the collective’s long-term projects, namely State of Emergency (1998- 2017) and While Having Soup (2015–present), this paper examines the strategies employed by the artists to stage encounters and how they used the rallying potential of art to activate public spaces and to ensure that they remain open to free expression and democracy. This paper also discusses the material and immaterial traces left by these public interventions.