Doesn't look like any tricks have appeared. I presume you have tried pushing while turning. Maybe you could pull the piece, turn it upside down, and pour in your favorite limescale remover.
Looking up "touch down drain" shows that they have a replaceable assembly that seems to incorporate the drain stopper and the tailpiece. It seems to be a Danze term. I also find the term "pop up drain" for items that look similar. http://www.homedepot.com/p/Vigo-Pop-...02CH/202863522 Also "umbrella drain" looks like it might be compatible. http://www.homedepot.com/p/DANCO-Bru...9467/100533760