I imagine residential ones are like our RV ice makers, in that if we unplug, break camp, and travel just after the unit cycles and fills with water, before it can get frozen in the tray some gets splashed onto surrounding parts and freezes there. Part of break camp routine for us is turning off the electric side of the fridge (ice maker) an hour or two before hitting the road, or the night before. Since they say residentials can hold cold for quite awhile, I guess turning them off entirely while on the highway would be okay, or having an easy-access water shutoff valve in the icemaker line.
Joel