Dlc dosent mean the add on, its actually the downloaded version. So I'm a little thrown off......disk and downloads to my knowledge can play each other. As long as u have/own a copy/Version on ur system.
You have to have the same game to play against each other, it's like saying 'I have COD4 and my friend has Black-Ops, can we play MP against each other?' The answer of course is no, they are 2 different games, just like GTA IV and GTA IV EFLC.
this is tru for any gamel but the fact that its a disk versus dlc dosent matter. as long as its the same game..........now there is a set called gta completed i think a that has gat iv and both add ons.