As someone who has owned a Cummins powered Dodge truck for almost 12 years, I have hear this rumor a hundred times.
If you could show me some sort of information that shows your statement to be correct then I will apologize for questioning you and walk away. The old Cummins website, around 2005 era, clearly stated that Ford did not own Cummins. That may have changed as I do not see that information available on the new site.
Cummins has sold over 2 million B series engines to Dodge. I find it hard to believe that if Ford owned a part of Cummins that they would pressure Cummins to walk away from this business. I could see that maybe Fiat has another engine that they would like to replace the Cummins with but that would be a marketing mistake. The Cummins badge on the Dodge has sold a ton of trucks for them.