Originally Posted by Tummy

The Scheduling Reference Handbook addresses this on page 54.

"Occasionally SC assignments may report very shortly after the SC begins. As long as the report is at or after SC start it is a legal assignment....With extremely short report/push back situations, the Company has made a business decision and understands you may not be able to report by the Company's posted time. You are not expected to drive excessively fast, for example, simply to make the Company's posted departure."

I would fulfill your previous obligations. Then, I would promptly go to work. If that takes you more than 55 minutes, I wouldn't worry about it.