I've done it three times online in the last four months. You can transfer from Amtrak to CO online, without calling, and no certificate is mailed. The points are transferred from Amtrak to CO electronically. My transactions have averaged about a week to post in my CO account.

The Amtrak site is just wrong regarding Amtrak-CO and Amtrak-Hilton transfers. Both are electronic, and can be done online, despite the message about a certificate being mailed.