Lightning n Chemicals wrote:
But it does beg the question:  Was this a JHW3-led project from the get-go?  Did he plot/layout the stories and finish the art, with Rucka just adding the dialog afterward -- the classic Marvel approach?

I'm leaning towards that conclusion.  The JHW3 layouts were just so intricate and well-crafted, it's hard to believe that Rucka wrote a script beforehand with that art complexity in mind.  
I think you're reading too much into it.  I doubt this was done Marvel-style.  Rucka's had a hand in her conception from 52 to Crime Bible to 'Tec.  JHW3's own comments suggest that Rucka had a plan for the character that's since diverged now that he's taking over plotting and co-writing:

Are you going to find it difficult pushing on with the character without Greg?

Yes, it will be. Greg brought a definite sense of direction to the character and he knew where he wanted to take things, so, with his departure, it forces things to be reevaluated in terms of continuing the character without necessarily trampling on any ideas that he had for her future and still make stories that are relevant and matter in the bigger scheme of the character for generations to come. So, yes, there is definitely a bit of trepidation involved - at the same time, I feel, it's a challenge worth trying to meet.


That said, I don't think the duties could be split as neatly as writer and artist.  Rucka himself talks about the collaboration in the above-linked CA interview:
It was very carefully constructed. Jim and Mike and I spent hours talking about these things. I'd call Jim and say this is the issue, this is the sequence, this is what needs to happen. And he'd come back and say I have an idea for a design and a visual here. If you see the script it'll say pages 4 and 5, and it'll just say, "Jim, this is as we discussed -- this is that thing with the lightning bolts." Batwoman has been the most collaborative project I've ever done.

LH: So things like the lightning bolts and the paneling -- that's something you came up with collaboratively?

GR: Jim's design sense is incredible. It is quite literally the act of somebody trying to describe a picture to you. So I wrote that first script, and he said, I've got these ideas and it wasn't until the pages started coming in that I got it. And once I started seeing pages, it changed the dialogue... Once I saw the pages I was able to say, ok, let's roll up the sleeves and really make this work. So by the time you hit 755, you're looking at design elements where he says this is how I want to handle it, or, I have an idea, can you write to this? The American flag banner in the first part of "Go," where Jacob is in the poppy field, and the transition with the American flag in the background -- that was one where he said, "I have an idea!" And then said, "I went with a different idea," and I went, holy crap!