This apparently was successful, and Amtrak now accepts smaller pets in carriers as a regular service on many routes for a $25 fee.
Restrictions:
- max. weight 20 pounds combined, max. carrier dimensions 19" by 14" by 10.5".
- one pet per passenger
- Coach class only (not in sleeper cars etc...)
- maximum trip duration: seven hours
See details at
https://www.amtrak.com/pets