In a small bowl, combine chicken, lime juice, cumin and salt; toss well to combine.
Place 4 tortillas on a flat surface and spread each one with 2 tablespoons of bean dip. Top each with about 1/3 cup of chicken and then sprinkle each with 2 tablespoons of cheese; divide scallions over top. Cover with remaining tortillas and gently press down on each one.
Coat a very large nonstick skillet with cooking spray; place over medium heat. Cook quesadillas in a single layer until golden brown on bottom, about 2 minutes. Flip quesadillas and press down on them with a spatula; cook until golden brown on second side, about 2 to 3 minutes more. Remove to a serving plate and cover to keep warm (or place in oven); repeat with remaining quesadillas.
Slice each quesadilla into 4 pieces; serve with salsa and sour cream.
Yields 1 quesadilla, 2 tablespoons of salsa and 1 tablespoon of sour cream per serving.