Given the complexity and evolutionary nature of a System-of-Systems (SoS) entailing frequently changing goals and requirements, extended enterprise collaboration is needed. The idea behind extended enterprise collaboration consists in teaming up with other stakeholders in partnerships in order to manage the skills, risks and investments required to rush the product to market. However, collaboration is far from being trivial, as it is constrained by several challenges such as heterogeneity of stakeholders and their ways of working-let alone global crisis like COVID-19. Thus, an overview of these challenges from both academic and industrial perspectives would be beneficial. With this in mind, based on a survey, this paper provides a comprehensive overview that goes beyond the challenges, to consider the benefits of, methods for, barriers and bridges to efficient collaboration. The survey was conducted among research-active academics in the field of SoS engineering, and companies in the US and European aerospace and defense industries. On the one hand, the results show that in response to COVID-19, work agreements (clear policies, commonly used processes and procedures, tools interoperability, clarity around roles and responsibilities of each collaborating firm, and proper change communication) are required in order to reduce uncertainty. On the other hand, it was revealed that "human bridges" are the backbone of extended enterprise collaboration. It is, indeed, human factors that either impede or promote efficient collaboration. An important finding that comes in agreement with recent calls for shifting the focus from "technology-centered" to "human-centered" SoS engineering.