This paper studies how vertical integration, subsidies, and interoperability regulation shape investment and welfare in electric vehicle (EV) public charging markets. We model the interaction between Charging Point Operators (CPOs), which invest in charging infrastructure, and Mobility Service Providers (MSPs), which sell charging services to end users. The model features indirect network externalities: denser infrastructure reduces range anxiety and increases EV adoption, while higher EV demand raises infrastructure profitability. In the benchmark laissez-faire environment, vertical integration creates a trade-off. Integrated CPOs-MSPs may foreclose rival MSPs and reduce downstream competition, but they also internalize the complementarity between infrastructure investment and EV demand, generating higher infrastructure density, EV adoption, consumer surplus, and welfare than vertical separation. This welfare ranking is established under foreclosure and is then generalized in a robustness extension with interoperability constraints. Minimum-margin rules keep the rival MSP active and soften foreclosure, while the integrated firm still retains part of its investment advantage. However, when interoperability entails compliance and coordination costs, stricter access regulation may further weaken infrastructure investment incentives. We also compare consumer subsidies and firm subsidies within the benchmark environment. Consumer subsidy dominates under vertical integration, while firm subsidy may dominate under separation only when network effects are sufficiently strong. A calibration to Italian metropolitan areas supports these mechanisms and highlights a fiscal trade-off: consumer subsidy generates larger welfare gains, whereas firm subsidy may deliver higher environmental benefits per euro spent.