I don't live in the N'east anymore, but even here in Georgia, we get a few weeks of deep freeze. I do whatever I have to do to ensure that there is access to water 24/7, including hauling hot water in Aquatainers from my house to dump into an insulated tub.
I don't normally say "Get out of dodge" but when a barnowner thinks water access isn't important, tis time to pack up and depart.
<>< Sorrow Looks Back. Worry Looks Around. Faith Looks Up! -- Being negative only makes a difficult journey more difficult. You may be given a cactus, but you don't have to sit on it.
If it was once or twice, or even for a week I wouldn't be worried. As a permanent situation, I wouldn't like it. Why can't they get heated water buckets on heavy duty extension cords for the winter? Troughs that they have already installed went dry? Sounds like laziness to me. My horse wouldn't be there long.
First of all I do provide water for my horses year round, heated in winter. However for many years I did not provide water outside in the winter. They were out for about 7 hours. I never had a problem. I also remember with my first horse, 40 years ago, horses were given access to water twice a day. They would each drink a couple of buckets. I know this is not ideal but this was common practice at other stables also and horses did survive.