No, but I have found a couple cameos and references to GTA3. Remember in the beggining where Catalina and the main character are dating? You are actually "going out" with Catalina in this one, and you do a few missions for her. In the last one she gets HELA pissed and leaves you for the GTA3 main character, but not before trying to smash your head in with a tire iron in a funny cutscene.

Oh, and I've now gotten for enough to learn martial arts to replace my boxing.