If the B and C properties are owned by the same family it stands to reason they could connect to B's old well and use a cistern/holding tank system to improve water pressure. As these are all mobile homes I don't see the need for large amounts of water (i lived in camper/trailer etc a good part of my life). If freezing occurs or somethings springs a leak and causes damage who would be liable for the damage? Who would be responsible for maintenance? If A is providing the power to the pump how would B and C reimburse A? Is A's pump up to providing water to all 3, and if it was found out after the fact who would have to pay for an upgrade?

It sounds like they could solve their own problems with a little effort and expense but are only to happy to get someone else to shoulder the burden.