With the growing concern over global climate change, the pace of transportation electrification has greatly accelerated in recent years to achieve net-zero greenhouse gas (GHG) emissions. However, electricity is not entirely generated from renewable resources at the moment. The overall carbon emission per kWh of electricity fluctuates due to the inconsistent nature of renewables such as solar and wind. How to utilize the low-carbon electricity remains a challenge. On the other hand, current designs and research on charging infrastructure separate electric buses and passenger cars, neglecting the great potential of coordinated charging between different transport modes. How to deploy and operate public charging infrastructure to best serve an electrified multi-modal transportation system while maximizing the benefits of decarbonization remains unclear. This research tries to integrate different transport modes into the strategic planning and design of the shared charging hubs to produce an efficient and low-carbon electrified transportation ecosystem. Shared charging hubs can provide holistic energy management to maximize GHG emission reduction given budget limits while balance peak power demands by integrating real-time electricity carbon intensity (ECI) and vehicle-to-grid (V2G) technology. The model was successfully applied to bus fleets of seven transit agencies and the park-and-ride cars of twelve rail transit stations in Contra Costa County, California. This research will help policy makers and transportation agencies make more informed decisions regarding the planning and design of charging infrastructure.