A PBO is a temporary organization formed by assembling members with diverse experiences and backgrounds, aimed at achieving specific innovation goals. Constructing a reasonable communication network structure and enhancing organizational synergy are effective ways to promote the sustainable development of the system. This study, based on the Input–Process–Output (IPO) model and social network analysis, utilized a group collaboration platform to conduct a three-stage communication experiment on 685 construction project managers. Under two organizational sizes, the internal mechanism of how communication networks with two levels of centralization influence task performance were tested. The results indicate that in the case of a smaller organizational size, PBOs using a decentralized communication network tend to achieve higher task performance. However, as the organizational size expands, PBOs employing a centralized communication network may surpass in task performance. Additionally, we found that with the expansion of organizational size, bootleg innovation behaviors of organizational members are continually stimulated, further enhancing collective task performance. This study, based on the evolution of communication network parameters, explores the structural characteristics of organizational communication networks and the mechanisms underlying the emergence of bootleg innovation behaviors. It delineates the key pathways for improving collective task performance. The findings can provide a scientific reference for the organizational evolution and development of engineering project management.