Are these possible?

Are any of these 5 achievements still possible to obtain?

Bounty Hunter, Dive Bomber, Emergency Room, All Alone, or Don’t Touch That!

All of them require the Defiant DLC, or the Anniversary Map DLC which I have but considering the current playlists is it even possible to get these achievements? The Anniversary ones requires me to play game types that aren’t in either of the CE Anniversary Playlists. So I’m wondering maybe if I go into a different playlist as long as everyone in the game has DLC, DLC maps will show up right? I’m sorry if this all sounds confusing but if anyone could shed some light on my situation that’d be great.

As far as I’m aware there are no unobtainable achievements in Reach. You are correct in saying that the DLC maps will come up if everyone in the lobby has them. However, not many people do. I’m pretty sure a majority of players don’t even know they’re free. One option is to create a gaming session on TrueAchievements. There are people who are still interested in going for those achievements.