I'm a PC player, but from my experience, yes.
The bare-bones game does not require an internet connection at all. It will ask for it when you start it up, but you can just pull out the cable and run it without.
However, the moment you install any kind of software DLC on top your product, the game will want to confirm with the server that it is indeed registered to your account on start-up. If it can't make that connection, all DLC related items, quests, locations and characters are 'removed'.
For example, my game sometimes has trouble communicating with the server and I've installed the free resurgence DLC. It gives me a few new weapons, maps and characters in Multiplayer. When the server fails to confirm this, all these new characters, maps and weapons dissapear from use, even though everything else is still there. When I reset the connection, they come back again.
For single player? That means that they will either not show up when you load the game, or the game outright refuses to load a savegame with DLC associations.
Rest assured though. This check is short and nearly painless. It will just want a minute to confirm your purchase on start-up and once it has done that, it will no longer require internet access. You can yank out the plug again untill the next start-up. Unless you want to MP of course.
Edited by Skirlasvoud at 02:36:42 05-05-2012
#8666388, By Skirlasvoud Mass Effect 3 *SPOILERS THREAD*
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