I did this and got an invite email within 15 minutes.
Apple is restricting them so it’s only Halo MCC right now. And it’s xCloud only, no console streaming.
I actually had poor results with console streaming, it was pretty laggy. I played some on this xCloud test and it was amazing. Loaded MCC, my Halo CE save from my Scorpio is right there. I’ve never played Reach so I loaded it up. Controls are responsive, graphics look sharp. I’m sold. This will be pretty amazing once they add all the games you own and GamePass.