Dave brings up a possibility that is less intrusive than “naming rights” – namely, companies providing services on board, which would enhance the voyage (& therefore the overall Amtrak image) at no cost to Amtrak, “for promotional consideration”.
In the 1970’s, several times I had the pleasure to ride the crack SNCF/TEE train from Paris to Marseille and Nice, Le Mistral. From 1969 to the early '80’s (when TGVs took over), Le Mistral used some very fine equipment (boilt under license from Budd, by the way). This included a unique “bar car” (in addition to the 2 full diners).
This bar car was one-half bar. The other half is what was unique. It contained a hair salon/barber (for both men & women), a boutique (where you could buy the latest newspapers & magazines, a new tie or scarf, stationary supplies, as well as souvenirs or something to take home to the family), and the “secretarial service” office.
This “secretarial service” consisted of trained secretaries and a bunch of office equipment, where you could (for example) copy a document, or dictate a letter and have it typed up before you got off the train. The kicker – it was, as I recall, all at no cha