This paper examines part of the participating research developed at the Healthcare Basic Unit (UBS) of São Paulo city (Brazil), whose aiming at understanding the implementation aspects of the Family Healthcare Program (PSF) as a public primary care policy, facing the hegemonic assistentialist medical model within the country. It shows possible articulation elements between the participating intervening research and in-service education, shaping a research proposal where participants' cooperation defines its own development and unfolding. Finally, it brings two examples of the UBS day-by-day, prioritizing: a) the political dimension of the knowledge-power relationships within the PSF teams and between these teams and other professionals working at the unit, and b) the ideological dimension by means of the representations of themselves and the other people in the working relationships, considering the identity/alterity dynamics. Among others issues, the analysis reveals the centrality of the healthcare community agent (ACS), who impersonates an intermediating role between the public healthcare system and the users from the city low-income neighbors/communities. This bordering place of the ACSs encounters and denounces the contradictions and stresses of a policy whose goals are defined without considering the popular experience/knowledge, that really reinforces the places of the governmental knowledge-power.