To put simply: You only get the DLC that was included in the individual releases of the games. The exception is Pinnacle Station, which is now included in the Trilogy because it's no longer available separately.
@Fred_vdp Are you sure about Pinnacle Station? As far as I know you still can get the DLC through Origin if you redeem the Steam or CD key of ME1.
I didn't get Pinnacle Station when I redeemed my CD key, but that was back when Pinnacle Station was still available for purchase. It's possible you can now get it when registering a product key. I hadn't considered the possibility.
