The posts for best strength would be attached tot he framing system, not to the deck surface nor the "cement board". These can either be bolted inside or outside the outside rim boards. Post up pics for better or more advice.

So this is what it would look like being on top. The bolts go all the way through to the frame either way we go. The other way the limestone would be cut around the post.

Bolting through tile looks like a leak and crack factory to me. Let the tile guys figure a way around the rail posts. Don't make the rail post guys figure through the tile please.