So, I've now encountered that ending that everyone's been talking about. When I played through it, my reaction was, 'Meh'. Later on, it dawned on me that none of this made any sense, and some web-browsing confirmed my suspicions about it being nonsensical.

Later on, I had an idea. One way to check whether or not it was a complete ass-pull might be to go back to ME1 and see if any of the events there made any more sense in light of the ending. So I did that (plus there were a few character classes I hadn't explored, so I thought it might be interesting).

And one thing did jump out at me, actually - the relays glow blue.

Make of that what you will!