Similar situation here, the shuttle leaves daily and is timed to connect the TE to the SWC. So heres my situation at Christmas. Were leaving our car at Galesburg taking the the SWC to LAX. On way home were taking the SSL/TE Lax to SPI. The SPI GBB shuttle would have been perfect to get back to our car in GBB.
Amtrak wont sell it to us because were not connecting to the SWC and the shuttle company cant sell tickets as Amtrak charters all the seats on their van. Another lost revenue and customer service let down for Amtrak
still looking forward to our 5 nights on the train.
Truth be told it turned out for the better. Enterprise will pick us up at SPI rent us a one way car rental for the 77 dollars tax included and the Enterpise is in the Amtrak parking lot in GBB. Im assuming its alot cheaper then the shuttle for 3 even though I couldnt even get a price quote.