I believe that a raven is smart enough to do it. Trouble is I also believe that they are smart enough to know that nobody is listening to them. For learned behavior to develope it would have to pay off once in a while.
Some people do seem to be genetically incapable of going past a gutpile without looking at it, and I suppose that ravens could have deduced from that that people are following them around. Other predators are definitely attracted to the circling ravens, I've called coyotes using only raven sounds. Given eons, the birds could have made the connection between attracting predators and getting fed. Alternately, given a great deal of time the Indians could have just seen the makings of a good story.
Its interesting to think about, even if I think that they are likely just already on a food source.
In an unrelated note; has anyone else noticed that when there's ravens, crows or magpies there is often a gut-pile, but when there's an eagle in the mix there's usually some red meat involved? I've seen that one over and over, whether its lost deer, or shot coyotes. You can make money betting on that one.