The proliferation of market-based public service delivery raises concerns whether the vulnerable are dully served and what mechanisms facilitate to serve them well. Focused on the availability of specialized substance abuse treatment programs for co-occurring, HIV, criminal and pregnant patients, this study adopts the dimensional publicness theory to examine how different dimensions of political authorities facilitate the provision of specialized programs for vulnerable groups. The multilevel analyses indicate that public funding and accreditation are two major dimensions promoting specialized programs. Environmental publicness exercises significant impact, contingent upon statewide policies and facility ownership. Differential effects are found both within and across dimensions, calling for a contingent approach to better understand both the theory and its implications.