Electric connected automated vehicle (CAV) shuttles as a part of sustainable microtransit system have the potential to fill public transit service gaps. Following technology and traveler acceptance tests that are underway around the world, mass produced CAVs will be considered for shared mobility service, including “first/last mile” travel between public transit hub stations and medical campuses or other activity centers. There is a need for knowledge on treating risk in such applications. This paper covers planning and economic feasibility of advanced technology level 4 automated vehicle-based microtransit system considering uncertain service and economic feasibility factors. Methods are advanced for addressing uncertainties in travel demand, service factors, and economic feasibility of investments by public and private sector entities. Specifically, a probability-based macro simulation approach is used to treat demand and supply-side service factors as stochastic and is adapted for risk analysis in financial decision making. The effects of uncertain life cycle costs on fares and rate of return are described. Results are favorable regarding the technical and economic feasibility of advanced technology-based microtransit first/last mile service. The findings reported here are a contribution to knowledge on feasibility of implementing CAV-based first/last mile and other microtransit services under uncertainty.