Public
...but only in the US, since Penguin in the UK decided that the expense of publishing it here wasn't worth the potential return.
Here's it's Amazon.com listing. The heavy discounting there makes it quite likely that I'll buy it anyway, although as it weighs three pounds the postage will add a fair bit. As you can see from the previews on that page, the illustrations really are lovely; Richard Adams was apparently delighted with them.
Aldo Galli, who did the paintings, is an active member of the WD discussion group that I moderate, so there's a particular reason for me to want to buy this. (He's a very nice guy as well, which doesn't harm things any.) This year is the 40th anniversary of the original publication of WD, and this edition commemorates that. I suspect they'll get quite a few buyers from the UK, which just makes me all the more irritated with Penguin UK.