...well, indirectly but that's good enough for me.
In an article I wrote about SeaWorld's science claims, I came to the conclusion (after running an extensive literature search) that, considering SeaWorld are supposed to have been studying orcas for 50 years, there just wasn't enough of it. I found that SeaWorld had only produced a maximum of 30 orca-related papers in all the time they have been holding orcas captive.
Since writing the article, SeaWorld have produced one more paper entitled Evidence for vocal learning in juvenile male killer whales, Orcinus orca, from an adventitious cross-socializing experiment. If you read the abstract, you will see their results "provided evidence that juvenile male killer whales are capable of learning new call types, possibly stimulated by change in social association".
Orcas with different dialects, from different populations, have been forced to communicate with each other in artificial environments for five decades. We already knew they were capable of vocal learning. This is how they come to use their population's dialect in the first place. They learn it.