The integration of Artificial Intelligence (AI) in the construction industry presents significant potential for improving efficiency and sustainability. However, adoption remains limited, particularly in the field of underground engineering, due to sector-specific barriers. This study investigates how company size shapes the opportunities and risks associated with AI implementation in the German construction sector. Focusing on small and medium-sized enterprises (SMEs), large firms, and public clients, the research is based interviews with experts from 20 companies specializing in infrastructure. The findings reveal a divide: while larger companies benefit from robust resources and structured data ecosystems, SMEs often demonstrate greater agility and openness to innovation. Common challenges include fragmented data standards, low stakeholder acceptance, and legal uncertainties. The study emphasizes the need for a unified digital foundation and active client engagement to ensure inclusive and effective AI integration. These insights contribute to the broader discussion on digital transformation and support the development of resilient and intelligent construction practices for sustainable built environments.