The official website of the XXXHOLiC Rou Adayume OAD was updated to inform that the after-recording sessions have ended. According to the website, the new OAD will cover the episode of Doumeki as a child.
The website also has a few screenshots of the upcoming OAD. You must click on the “screenshot” button written in japanese in order to see them (4th button).
The OAD will premiere on February 6 at the CLAMP@MOBiLE Fes! 2011 special event. A promotional movie is expected to be released soon at the official website.
This website has a preview of the Koukan-Nikki doujinshi in which CLAMP participated as guest artists. You must click on the “Hai” button in order to see it (1st button).
Lastly, I don’t know if this information is any helpful for anyone but Animate is selling a clearfile with the crossover illustration from the CLAMP@MOBiLE Fes! 2011 poster. Not sure if they deliver overseas but this can be an easier way of having a clearfile (not a poster) with that illustration without having to attend the @MOBiLE event.