http://www.capitolcorridor.org/blogs/get_on_board/issue-26-july-7-2006/
Joint Ticketing with San Joaquin trains
As an added bonus, by arrangement with Caltrans (California Department of Transportation, Division of Rail), all passengers between Oakland and Martinez will be able to use any train operating between those two points using any valid Capitol Corridor or San Joaquin ticket. For riders in this busy part of our corridor, this will offer you 20 trains per weekday in each direction, or 40 weekday travel choices. San Joaquin trains stop at Oakland, Emeryville, Richmond and Martinez. They DO NOT stop in Berkeley. These San Joaquin trains will now be shown in the Capitol Corridor Timetable as a convenience to our riders.