Why would you switch at all? Why not have cabs that can do both?
The load/range regimes are so different that there might be a case for specialist units, especially if there is an artificial incentive (like congestion charging) to use low emission vehicles in the city. Long distance motorway work needs a 300kW continous power plant with 3MWh net fuel capacity, whereas city deliveries only need 75kW continous/150kW peak and 200kWh fuel/battery, assuming charging points at loading docks to allow recharging during unloading.
The load/range regimes are so different that there might be a case for specialist units, especially if there is an artificial incentive (like congestion charging) to use low emission vehicles in the city. Long distance motorway work needs a 300kW continous power plant with 3MWh net fuel capacity, whereas city deliveries only need 75kW continous/150kW peak and 200kWh fuel/battery, assuming charging points at loading docks to allow recharging during unloading.