Plumbing problems in our two back to back bathrooms led to a complete redo of the common wall and the shower, bathtub area.
What a mess it was. The backer board that was in there was truly no good. It was coming apart like crazy.
Our plumber told us that Greenboard was the best thing out there for moisture areas like a shower or bath. I don't know if our plumber didn't know about concrete backer board or it just wasn't on the market. That's what we should have used. Anyway, we've moved since, and I don't know how the Greenboard is holding up.