The hospital where the employees quit is going to sue the new hospital for damages by hiring their employees at a higher rate.
And how will that be upheld? If an employer wants to pay more for the same level of work, that's their business.
Absolutely no idea. I assume that would be up to the courts. The argument I read was that by hiring away that staff at a higher wage you have caused damages to the corporation that lost the employees in the form of lost profits. That loss of profits could be recouped in a civil suit by the courts awarding damages.
No idea if that would fly, legally, but that was how it was explained to me.