Might be interesting if this touches qualified immunity for all state actors, like police and such.
I have not read the ruling but I think it likely it was found that there was a possible or even probable violation of inmate’s civil rights. Cases involving such violations are not protected by sovereign immunity.
There is also the whole duty of care which THE POLICE DO NOT OWE THE GENERAL PUBLIC. It may be that because prisoners are essentially obviously under the care of the prison such a duty of care is owed.
Just supposition on my part mind you.