Some newer diesel engines have features where they can reduce down to only running a single cylinder when parked/idling to keep the electrics running as expected to greatly reduce fuel consumption and emissions while idling which might help as that trickles into fleets

But yeah in reality these service trucks should be smaller electric vehicles for local delivery, or even better they should be electric trains pulling power directly from the grid. Heck I’ll even take diesel electric trucks with a pantograph to use power from an overhead wire instead of burning Diesel while in cities. Imagine if our roads had big networks of overhead wire to power trucks and buses from! Imagine if every hill on a highway had a section of overhead wire for trucks to power themselves off of while climbing. Realistically every transit mix will require some amount of trucks and buses so we might as well minimize their impact while we imagine a better world