In terms of risk management, I do not believe that it is practical to notify before arriving at the border. There are many potential options to deal with the problem ahead of time. If there is a sick person on a bus, you can notify the border officials, but if the situation gets worse, you could take that person to a hospital before arriving at the border rather than keeping him or her on the bus.
On April 18th, 2007. See this statement in context.