Interviewers at MBB usually receive the CV and cover letter of candidates. However, the specific information that interviewers receive may vary depending on the office and the recruiting process.
That being said, it's important to keep in mind that interviewers typically use the CV and cover letter as a starting point for the interview, but they will also ask questions about your experiences and skills that go beyond what is written on paper. So, while it's important to have a strong application, you should also be prepared to speak to your experiences in more detail during the interview process.
Best of luck in your application process!