A focal point in the "Smart Mobility Strategy" published by the European Commission is the expansion of public charging infrastructure as a key driver for the electrification of the passenger vehicle stock. Quantified targets have been set for the coming years. In the scientific literature, the geographic allocation of charging stations and the short- and long-term expansion of public charging networks have been frequently studied. These studies typically emphasize high geographic resolution of street networks and traffic flows, while assuming an exogenously determined electrification pathway for passenger cars. Another strand of literature focuses on modeling the adoption of battery-electric vehicles (BEVs), based on detailed representations of consumer decision-making, as well as developments in costs and technical performance. The objective of this work is to bridge these two perspectives by modeling the interaction between charging infrastructure expansion strategies and vehicle adoption. This is done from the viewpoint of a policy-maker operating at the federal state level, aiming for system-cost-optimal decision-making. We focus on two crucial aspects of public charging infrastructure expansion: network density and expansion speed. Additionally, we analyze income-dependent adoption behavior and cross-regional effects between subregions of a federal state. The case study is the Basque Autonomous Community. Preliminary results indicate that early increases in charging site density have a significant positive impact on BEV adoption, particularly among the middle-income population.