I think the chances of someone being able to cite a real-life business example that is genuinely a good fit / proof of what you are recommending - rather than something you are trying to shoe-horn into the interview - is pretty remote. So it's likely to back-fire on you. The case study interview is about seeing how you think through problems and interact with the interviewer (client) to reach a well-considered solution. So focus on this - and save demonstrating your business case knowledge for the broader "experience" interviews you'll also face.
If you'd like to feel more confident about tackling the case study interview then you're welcome to join in the next call I'm running on the subject this Friday. Details at:
<a href=http://events.top-consultant.com/UK/careerconference.aspx?ID=140 target=_blank>http://events.top-consultant.com/UK/careerconference.aspx?ID=140</a>