I don't think Amtrak's long distance management cares about BART connectivity for the Starlight. If they did, they would have kept Richmond on the line. According to others on this board, the reason Richmond was dropped was because chronically late northbound trains would arrive after the joint BART/Amtrak station was closed, necessitating expensive taxi rides for passengers. If Amtrak cared about BART, it would be a no-brainer to keep Richmond on the line for southbound trains – the morning arrival isn't a problem and it would be a seamless transfer to pretty much any destination in the Bay Area (factoring in a transfer to Caltrain at Millbrae).
The Coliseum station is not an ideal transfer point for BART, particularly at night. It's a rough neighborhood, and public transit facilities have effectively become homeless shelters in the Bay Area. It's also a hike from the Capitol Corridor station to BART. It's fine if you know what you're doing and you're used to navigating Bay Area public transit, but if you tell the proverbial Little Old Lady from Pasadena that all she has to do to get to, say, San Bruno is hop on BART at the Coliseum, it would not end well. It would be a safer bet to tell her to get off at Jack London Square, hit the bars and see if she can get lucky
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