Preheat the oven to 450 degrees F. Combine the lentils, squash, bay leaves and 2 1/2 cups water in a saucepan. Bring to a boil, then reduce the heat to medium low, cover and cook until tender, about 25 minutes.
Meanwhile, mix the mustard and thyme in a small bowl; brush all over the pork. Place the pork on a baking sheet and sprinkle with the breadcrumbs. Transfer to the oven and roast until a thermometer inserted into the thickest part registers 145 degrees F, 20 to 25 minutes.
Meanwhile, combine the bacon, shallots and celery in a medium skillet and cook over medium heat, stirring occasionally, until the bacon is crisp and the shallots are golden, about 8 minutes. Add the wine and cook until it evaporates, about 5 more minutes. Stir in the parsley.
Remove the pork from the oven, cover loosely with foil and let rest 5 minutes. Divide the lentil mixture among plates. Slice the pork and serve with the lentils. Spoon the bacon mixture on top.