Gosh dang it! You just discovered part of my secret pork rib rub! LOL!
Old bay seasoning works very well as a BBQ rub just look at the ingredients, celery salt, mustard, red pepper, black pepper, bay leaves, cloves, allspice, ginger, mace, cardamon, cinnamon, and paprika.
All of those ingredients are included in most commercial BBQ rubs in some measure or another.