I believe Liberty has taken possesion of the Art Nouveau/Deco territory with their line.
Art Nouveau features so prominently in Liberty's history (Arthur Liberty was instrumental in the development of the Art Nouveau movement, through his encouragement of its designers), that it was inevitable, that, at some point, they would reproduce it again and I think the result is, characteristically, lovely and demonstrates how one can, successfully, draw from one's past.
However, as you no doubt know, Art Nouveau was such a huge movement in the late 19th - early 20th Century and its late 1960s and 1970s reincarnation so long-lived and widespread; that I don't think Liberty can even begin to own the entire Art Nouveau territory.
Liberty aren't even alone - Art Nouveau also, fairly recently, featured in the Miu Miu A/W '04 and Roberto Cavalli A/W '06 collections (and perhaps also others?); but I think there's still plenty of room for much more, particularly from Biba.
Art Nouveau inspiration is almost as prominent in Biba's history as the original Art Nouveau movement is in Liberty's; Biba's original logo was Art Nouveau-inspired, after all. The only real differences being that Biba's Art Nouveau influences were, very much, via the mid-to-late '60s - early '70s, of course, which, inevitably, gave it quite a different feel and that, unlike Liberty, Biba isn't
really Biba anymore; so they aren't really drawing from their own past, but from someone else's.
In fact, Art Nouveau motifs are so, inexorably, linked with Biba, that many people, who are not aware of the original movement, appear to associate Art Nouveau,
entirely, with them. A recent example - when Roberto Cavalli produced his Art Nouveau-inspired print, the general assumption seemed to be that he had ripped-off Biba!
I think that by not addressing this association (and the later Art Deco association), Biba are missing a massive trick. Yes, some people may complain that it is too obvious and/or derivative - but that is, surely, the whole point of reincarnating a line like this, in the first place (not to mention the essential point of modern fashion, in general!)?
There is no point in steadfastly avoiding the obvious, if the obvious is the most attractive and relevant option.
If their intention was never to reproduce Biba, as it is best remembered, or, at least, as a modernised version of that; why on earth did they bother buying the rights in the first place, I wonder?