I haven't seen a dlc map in over 20 hours of multiplayer game play. Doesn't even come up as an option to vote for next map. I've seen others have this issue, but haven't seen a resolution discussed yet.
They should simply offer the map pack for free and advertise it everywhere within the game so that everyone knows to go download it. That should ensure that those maps become playable within the game because as it is now the chances that everyone within a lobby has them is pretty much nil which means that the people who paid to play them can't. I'd say that anybody who actually paid for them should be granted $15 worth in CoD points to compensate; plus, they've had them since they became available so they've been able to play them in custom matches if they wanted as an added bonus over those who would be getting them for free.