It's interesting that for publicity purposes in the making-of video (above) they have taken steps to disguise the digital origins of the drawings by adding some fake "flipping paper" effects to the animation.
I think I understand why this is done for the general public consumption: the minute you tell non-animation people "we used a digital program to do the animation" many people have this crazy idea stuck in their head : "ah-ha, the computer does it all" , as if the someone simply types in a command and pushes a button , then the computer program animates the scene. Whereas people still understand that if something is hand-drawn an artist is responsible for creating it.
It is difficult for many people to grasp the idea that there can be hand-drawn animation made on a computer , which is virtually the same process as hand-drawn animation on paper, except the lines are drawn directly into a program like TVP Animation using a wacom tablet, instead of drawn on paper and scanned/photographed.
Some additional comments from the director/lead animator, Hans Jorgen Sandes, were posted on the TVP Animation Community User Forum: