Will there be road closures as a result of the predicted tidal power outages, ostensibly to prevent looting, as happens with other disasters?

This could well happen. It will be a case-by-case decision. But around large cities, high crime areas where there is concern about civil disobedience on top of looting and opportunistic thefts, there may well be a safety crackdown, even invoking martial law, depending on how the citizenry reacts, and that will be a moving target. Over time, as people are confined and suffering, all bets are off on how bad things might get. Keep in mind the Extraterrestrial Alliance will be beaming mind control suggestions of all kinds to induce acting out behavior and extremely emotional overreactions to the feelings of helplessness engendered by a loss of central power and all that means in making people helpless.