I'm surprised you didn't know.That's kinda funny. I heard about Reach coming to pc but since I never looked into it, I assumed that the news was about the Reach being added as the last remaining game, not as the first.
No. They launched with only Halo Reach in the PC MCC last December.
They added Halo 1 in March.
Still waiting on Halo 3, ODST, and 4 to release on PC.
If you buy it, each game is separately downloadable. (Although of course, most of it isn't available for download yet).