Will this have a case study?

I'd think that, at the very least, they would ask lite cases, which are often vague prompts that do not have any data or tables. 

These prompts are expected to take ~10-15 minutes and can take on a few forms: 

- Market sizing questions:

• Basic: What is the market size of automobiles in Canada? 
• Intermediate: How much money, in tips would a cab driver in New York Make? 
• Advanced: How many students, annually, would attend MBA programs in Canada? How much annual revenue would be collected?

- Factoring: 

• Basic: What are the factors to consider for an organization change? 
• Intermediate: What factors would you take into consideration for the implementation of a new enterprise-wide internal CRM tool?  
• Advanced: What factors would you consider in succession planning for a new senior leader (think CEO)

Now, the above are hypothetical cases that I have seen given at early points of the interview process or at the Partner chat of the interview process. You may very well receive people advisory oriented cases targeted toward utilization rates, learning & development, facilitation of internal tools, processes, organizational effectiveness prompts, and other categories traditionally covered in people advisory. Whether or not you receive those cases, in either take-home form, or in a 30-45-minute interview, is dependent on the team and office as well as the firm. 

I would steer on the side of caution and try to speak with other colleagues and see what they received; or assume you'll receive something like a case prepare from there.