Bring a large saucepan of salted water to a boil. Add the green beans and cook until crisp-tender, 5 to 7 minutes; drain. Meanwhile, toss the jicama with the cilantro, half of the lime juice and a pinch each of cumin, salt and pepper. Let stand 10 to 15 minutes.
Heat 3 tablespoons olive oil in a large skillet over medium-high heat. Add the cremini and oyster mushrooms and cook, undisturbed, until dry and golden around the edges, about 10 minutes. Stir, then continue cooking until well browned all over, 8 to 10 more minutes. Push the mushrooms to one side of the skillet; add the green beans, remaining 1 tablespoon olive oil and remaining 1 1/2 teaspoons cumin to the other side. Season with salt and pepper and cook, stirring the green beans with the mushrooms, until lightly browned in spots, about 3 minutes.
Mash the avocado with a pinch of salt and the remaining lime juice. Divide the vegetables among the tortillas; top with some of the jicama, the mashed avocado and more cilantro; drizzle with hot sauce. Serve with the remaining jicama.