Pat the beef brisket dry with paper towels and place it on a cutting board or large plate. Trim any very thick or hard pieces of fat, leaving a thin layer for flavor.
In a small bowl, combine the chili powder, smoked paprika, ground cumin, garlic powder, onion powder, dried oregano, fine sea salt, and black pepper. Stir until the spices are evenly mixed.
Rub the brisket all over with olive oil, then sprinkle the spice mixture over the meat, pressing it gently so it adheres to every side and surface.
Preheat your oven to 300°F (150°C). Place the seasoned brisket in a baking dish or roasting pan. In a separate bowl, stir together the BBQ sauce and beef broth, then pour the mixture around the brisket in the pan.
Cover the pan tightly with foil and bake for 3 to 3.5 hours, or until the brisket is very tender and can be easily shredded with a fork.
When the brisket is done, transfer it to a cutting board and let it rest for about 15 minutes. Use two forks to shred the meat into bite-sized pieces, then spoon some of the pan juices over the shredded brisket to keep it moist.
While the brisket rests, prepare the elote-style corn. Melt the unsalted butter in a large skillet over medium-high heat. Add the corn kernels and cook, stirring occasionally, for 6 to 8 minutes, until the corn is hot and lightly browned in spots.
Transfer the warm corn to a mixing bowl. Add the mayonnaise, sour cream, crumbled cotija cheese, lime juice, chili powder for elote, and fine sea salt for elote. Stir until the corn is evenly coated and creamy, then fold in most of the chopped fresh cilantro, reserving a little for garnish.
Warm the corn tortillas in a dry skillet over medium heat for about 30 seconds per side, or until soft and pliable. Stack them on a plate and cover with a clean towel to keep them warm.
Assemble the tacos by placing a generous spoonful of shredded BBQ brisket in the center of each warm tortilla. Top with a scoop of the creamy elote-style corn.
Finish each taco with a sprinkle of the remaining crumbled cotija cheese, chopped fresh cilantro, and thinly sliced green onion. Serve the tacos with lime wedges on the side for squeezing over the top just before eating.
Serve the BBQ brisket elote tacos right away while the tortillas are warm, the brisket is tender, and the elote-style corn is creamy and flavorful.