I'm not sure about that particular dialect, if it's case or not, but it's a fact that some dialects do keep the dative (though it's been disappearing somewhat recently). In addition to certain country-wide expressions which have kept old case forms, like "gå mann av huse", and "i live" (being alive), though I've recently seen so-called "journalists" in newspapers being unable to understand it and writing "i livet" instead, which has a totally different meaning.