Marriott & SPG will officially merge on 1 August 2018. ACS has a large number of transfer partners that are not partners with Marriott, one is amtrak, and they are without advertising the fact that on July 31, 2018, will be the last day to transfer points in the program. Based on how to phrase it, I would be surprised if the Marriott points will be transferred to the Train, but I guess anything is possible. Transfer rate is 1:1, but You will not receive an additional 5,000 points when you transfer in chunks of 20,000, how are you doing with partner airlines & LNG so most people can not stand in the Train. There may be good values to be had, if You value points Amtrak, we discuss their estimation in more detail here. You used to be able to transfer chase UR points to Amtrak, but that was before 2015. I suspect that it was part of the Amtrak contract signed when Bank of America became co-branded card Issuer.
Hat tip ilessthanthreethis