Home run MF wrote...
With less than 9 months on the calendar, and little indication of how much creative control the DLC creators have had with respect to affecting the storyline of the upcoming chapter in the sci-fi epic, it might only have side-quest levels of consequences in the end. (Mass Effect 3 designer Manveer Heir has since told me that Arrival's story "was driven/approved by the head writer so it's all canon & relevant.")
Source: http://www.destructo...lc-197513.phtml
Yeah like I said, there's a few forms of 'canon' when it comes to Mass Effect.
Full Shepard (aka internal Bioware developer canon *cough*) = Arrival happened
Custom Shepard (aka up to your wallet if you wanna get those story developments explicitly shown and realized to you) = Arrival kinda sorta happened, and definitely happened if you bought and played the DLC
Default Shepard (aka you fool decided to ignore the rest of Mass Effect!) = Arrival happened somewhere else
But you know, Arrival still happened, lol. I think that's what CoolioThane was getting at.
Bioware may throw the player bones so that they don't think 'omg I didn't get a complete game!!QQQQQQQ', but really, the thing still happened.
Bioware just has story safeguards for those players who didn't want to pay for the content.
If Shepard got indoctrinated in Arrival, he also can get indoctrinated throughout ME2 or even ME1, depending on if they want to show us that story.
If Liara becomes Shadow Broker regardless of DLC, hey, it happens. We all know Shep really helped her with it, but yeah, we'll 'pretend' she did it alone.