I believe the the tube is pressed in just like the 42mm version. To remove it you need to get a fairly small rat-tailed file to stick inside the tub. You then press the file into the tube twisting as you go until you get it in there nice and tight, then start twisting and pulling out. You'll have it out of there fairly quickly. Make sure to tape off the rest of the case to prevent any scratches.
If I am wrong on the construction, I am sure somebody will correct me...