There would be cases as well. Good news is that the fundamental of solving a case remains the same, so if you are preparing for other consulting interviews, those efforts would be worthwhile.
The nuance is that DHL consulting focuses on supply chain and logistics. So it would be good to read up on the basics of this area. Get yourself a bit more familiar with at least some of the basic terms and operations, so you don't get caught off-guard during interview.
Last, read up some case studies, white-papers that they publish on their website, to get a feel of the work they do.
Hope it helps,