ALTERNE (Alternative Realities in Networked Environments) platform aims at providing a high level of integration between various techniques supporting mixed reality, graphics, interaction and behavioral models. This paper focuses on two collaborative aspects the platform provides. First, it contains a virtual object repository, which allows artists to share their ideas and support collaboration on projects based on ALTERNE platform. Second, it enables direct and remote access for public visitors to the artistic installations so that all concurrent visitors can cooperate on the exploration of the installation.