The part I find most intriguing begins at 0:35 in the clip. Robert Plant describes how in making this album he and Alison both intentionally stepped back from their usual roles while doing their own solo projects wherein they are in control and instead let someone else (producer T Bone Burnett) direct the creative process. They did this for the sake of the music. This is a nice example of established artists, who certainly bring longstanding habits and strong views of their own to a project, realizing that they each need to embrace a certain sort of humility in collaboration so that the music can be the focus and not so much themselves.
Here is how Plant put it:
We both removed our own producer hats that we have in our own worlds and gave them to T Bone Burnett [the album's producer] and so we were in a place that was quite magical; it was like a really, a new world for both of us.
I would say this illustrates another principle that is important when artists work together on a joint project: each collaborator must place his (or her) own ego aside and be willing to accept direction and ideas from others for the sake of the overall project. Each one gives generously for the sake of a shared artistic vision which, while not the sole possession of any single contributor, belongs to the group as a whole. The final artistic product benefits greatly from this sort of humility.