I've been looking at the same files. Apparently, Mafia II has a playlist system implemented for songs. Each song has an ID number, and playlists are kept in one of the files (as mentioned in OP) for each chapter, so that the songs can be played in a certain order. This was an aesthetic choice by the developers of the game, as they wanted certain songs to play in certain chapters to entertain the "mood" of the storyline in the game. It is possible to convert more songs into the correct file format, and "add" the songs to the song ID list and playlist files so that they show up, but I haven't figured out how to do it yet. If anyone could tell me how to edit the table files so that they do work, I'd highly appreciate it.
I also want to edit the traffic files for the game (CARM15DAMBIENT, etc)Â so that a wider variety of cars appear, as mentioned in the OP, but I can't, because the table files won't let you save them. I would like to edit the files so that older cars appear further into the game (like it did before the game was released), and also add the DLC cars to certain chapters so that they spawn in the game too. I was doing some digging inside the table files for the game in SDS Explorer, and I actually found a file that had the list for all the possible color combinations that cars spawn in inside the game, and I found out that all the DLC cars actually have more than one color combination listed, even though the three hotrods from Chapter 8 are the only DLC cars that actually use them, and all the other DLC cars only use one of the color combinations each. This consistently proves, along with the GDC 09 footage of Mafia II, that the DLC cars were originally supposed to be part of the actual list of cars in-game, but they were ripped out to be DLC only.