PREPARE THE BEANS: In a large saucepan, cover the beans with 2 inches of water and bring to a boil. Simmer over low heat for 1 hour, stirring occasionally.
In a medium skillet, heat the vegetable oil. Add the onion, garlic and jalapeño and cook over moderate heat until softened, about 7 minutes.
Add to the beans, along with the tomato, oregano and enough water to cover. Season with salt and pepper and simmer until the beans are tender, about 2 hours longer, replenishing the water if necessary.
MEANWHILE, COOK THE PORK: Preheat the oven to 300. In a small enameled cast-iron casserole, combine the broth with the garlic, onion, habanero and serrano chiles, bay leaf, cumin and » teaspoon each of salt and pepper and bring to a simmer. Season the pork loin with salt and pepper and add it to the casserole.
Cover with foil and bake for about 1 hour, turning the pork once, until tender. Transfer the pork to a plate and cover with plastic wrap until cool enough to handle.
Remove the bay leaf. Shred the pork into strips and stir into the broth. Season with salt. Fill the tortillas with pork and serve with the black beans and salsa.