SO annoying. I was just looking into this as it was announced, and read about it here:
So I poked around and found that there was (as of last week) a version of Ubuntu for tablets and phones. But does one access it? There were no .iso images or other easily-obtained distributions. Although there were a few pages blathering about potential partnerships for those who may be interested. So my guess is that it was only low-key released/escaped for a few developers but never given proper distribution generally. If so, their complaints about its lack of adoption sound like they were exclusively banking upon OEM deals instead of building a base of actual users.