Hi SeanTor,
Here's my personal story. I understand the scenario doesn't apply to everyone and some people may have an emergency AFTER their citizenship ceremony.
Anyway, I had an important family-related trip to make and booked a ticket before I knew I'll be invited to the citizenship ceremony. Luckily I had a couple of weeks to spare.
I informed the officer during the ceremony that I need the certificate urgently to obtain a passport. She was nice about it and understanding. She asked me to send her a copy of my flight ticket. She then processed the certificate the next business day and I received it by mail 3 days later. That same day, I filled up the passport application form, got it signed by a guarantor (a friend), got my photos taken and called the passport office informing them of the urgency to travel. They gave me an appointment in person the next day, and I went back to get the passport around 3 days after that. I received my passport just one day before my travel date!