Battery-swapping heavy trucks play a crucial role in developing green logistics parks, though their large-scale deployment faces challenges from limited grid access capacity at swapping stations. To address these challenges, this paper introduces Mobile Energy Storage Vehicles (MESV) as flexible dispatch resources within the truck-station system and proposes a comprehensive energy scheduling strategy for rigid heavy-truck load scenarios. Firstly, based on typical daily wind-solar-thermal power output scenarios, we establish a full-state transition model of MESV that incorporates coordinated charging/discharging constraints between plant and field sites, along with transportation resource limitations. Secondly,aiming to minimize total operating costs, we develop a mixed-integer linear programming method that simultaneously optimizes vehicle states, charging/discharging power, and transport arrangements. By integrating minimum feasible configuration determination with vehicle-discharge duration coupling analysis, we identify operational thresholds. Finally, multi-scenario simulations demonstrate that our strategy ensures temporal continuity of coordinated charging/discharging operations while achieving optimal balance between task completion time and operational economy under the minimum operational boundary, highlighting its practical value in grid-constrained environments.