openttd.grf is basically the same as ttdpbase.grf, only with some ottd specific stuff added to that. So the new openttdw.grf should basically work just fine in ttdpatch. Otherwise, just load openttdw.grf as a newgrf in patch (you might need to change the grfid first). Speaking about Bob's uncle.
Leave it up to me. As soon as the ottd stuff is finished, I'll knock out a version that works with Patch if it doesn't do that already.
Doesn't look much different to me.
Feel free to remain using the original TTD graphics then.
I don't consider OpenGFX a copy as in the definition of copy. It's even less of a copy than the Chinese starbucks implementation I saw a while ago in the funny pictures section (or was that engrish.com, anyways...). It's not even a derived work, because no single group of pixels  has been reused.
I agree that it's a similar work, but take the grass for instance. Is that similar to the TTD grass, or similar to the grass outside your window, with some gridlines added? 
Maybe we should get Atari's official statement on the new graphics. If it's something like "do whatever you like, we're not interested in TTD any more", we're completely off the hook. Forever. Or I could just buy the rights to TTD: "Whose baby is that", "What's your angle" and "I'll buy that".
If you look at single pixels, you'll probably find 100% of them reused, but that due to the limited palette colours.
Other examples might be more similar to TTD graphics than real world equivalents, but that's the other 50% I talked about earlier.