Perhaps you don't know anything about it. Dish actually feeds their ads on top of others. (Every now and then the timing is off so you can see that Dish interrupted another ad).
Apparently YOU DON'T KNOW, but that is common and has been done by local stations over network feeds for decades.
It is also common in radio where you are likely to hear a Rush Limbaugh or Sean Hannity commercial for a New York City business/product being dubbed over by a local commercial.