Hey, Proud Grampa -- No, the green board is not entirely going to be tiled over. Some of it will simply be smoothed out or sealed over, or whatever the term of art is. Yes, it has also been placed on the ceiling. The completely tiled-over sections unsurprisingly withstood the flood far better than any other part of my apartment.
Oh, and BTW, next time I'll know better than to wear black skinny jeans, a black sweater & black loafers when walking through an apartment that's just been dry-walled. I was rather floury by the time I left -- I looked like I'd been baking and had wiped my hands on my clothes. My shoes are quite whitened underneath. I left white footprints in the grass behind me.
Seriously, Gary, it can't be good to be breathing this stuff on the job, and I hope you have to wear a mask or something. Even if it's completely benign, with nothing at all toxic in it, I expected to be coughing and spitting it all night.

SAEF ....we always tell the "suits" that walk in on our jobs "DO NOT touch the walls! Your black suits will be white!"...wait until the mud starts flying! We can track white footprints for miles!!!