As much as its pain me to say, because they are playing the music of my childhood and young adult life, I think 'rhythmic oldies' is the most appropriate label for their format.
They're essentially a refresh of the jammin' oldies formats that started popping up everywhere 10 years ago. Instead of the disco/funk/R&B, etc.- they're playing more 90s rhythmic music. The concept is essentially the same, though.