I know that one article I read said they would put the fat into the animals blood vessel system, which dd not seem feasible.
From Food Beast...
This practice has been going on for at least 50 years, and involves injecting carcasses of beef with melted or powderized animal or vegetable fat (or a solution containing the liquid lipids) right after slaughter or in the butchering process. The fat then runs through the beef's blood vessels, creating a falsified marbling effect. Some more current research has shown these methods can increase the quality of beef by at least two USDA marbling scores. That's like taking a piece of USDA Select grade beef and upping it to Prime, the highest quality of beef, simply by injecting fat into the meat.
And I guess I am undecided on this one...So you can make it a $4 cut look and taste like a $24 cut, but as Anthony Bourdain put it, you are a "douche" for doing it. Why? I am trying to think of an analogy and I can't! Now, I do have an issue with calling it something it is not.
Sure, this beef would look and taste the same as its higher-quality counterparts, but the ethics behind it are still skewed. Restaurants can essentially get away with selling lower-quality, cheaper meat at a higher price since they can claim it's Prime, Kobe, or Wagyu and nobody would be able to tell the difference.