Things I would want to know (as a starter)
1) have they done this before?
2) If so when, where and how big a project?
3) if so what issues\problems did they see and how did they overcome them?
4) If no what do they expect the problems to be?
5) How do they will they go about the project?
6) What resources do they think they will need?
7) Ask general questions about how they organise their projects