Optimal grid-integration planning of a public transport hub (PTH) is an important way to improve the efficiency of urban transport and distribution network operation. Based on an in-depth analysis of the interaction mechanism between PTH and a distribution network, the potential contribution of PTH-based demand response to system operations under normal and contingency conditions are considered. A three-layer optimization model of PTH allocation for improving the reliability and economic performance of distribution system is developed. In the proposed formulation, the upper layer aims to minimize the total investment and operational cost of the network by optimizing the location of PTH placement and the number of electric buses/charging piles installed. The middle layer aims to minimize the PTH energy purchase from the distribution grid during normal operation, while satisfying customer demand for public transport service. The lower layer aims to minimize the outage loss of the system during grid supply interruptions by optimizing the departure intervals, load shedding capacity and charging/discharging power of electric buses. A multi-layer solution algorithm is designed to analyze the proposed model efficiently. Finally, simulation results based on the IEEE33 bus test system demonstrate that the proposed planning approach is capable of fully exploiting the potential flexibility value of PTH resources, while respecting both the economic and reliability criteria of system operations.