In general the interviews at Accenture are not that structured:
- No clear guidelines for cases, so the case depends on the interviewer
- 60% chance that it will be marketsizing
- 40% chance - profitability and general frameworks
- Interviews with the partners will most probably have no case at all
- Interviewers are less demanding than at Big3. unless you meet an ex-big3 consultant as an interviewer
- For fit I would prepare: Story about yourself; Why consulting; Why Accenture; Leadership; Team work; Your questions to the interviewer
In your case, applying for a senior manager role, will require mainly the functional knowledge and the good fit answers. You may have some case-type questions, but they would sound more like "How would you structure the workstreams and the team for this project?"