If you're a TR subscriber who participated in the private Homeworld Remastered Collection beta, you should be receiving a Steam key for the full game in your inbox soon. Look for an email from Cyril later today.
The full Homeworld Remastered Collection comes on out Wednesday, so the game won't unlock until then. You can activate the game on Steam via the key at any time, though.
Thanks again to Gearbox for helping make this very cool subscriber perk possible for the TR community!