Looking at the site you quoted most of the big "sells" are delayed publications which would mean (?) that most of the activity today has been buying hence the rise.
Probably on the back of the mounting coverage about TalkTalk, about how quickly they are getting their 0.5m customers online, their QoS, and the fact that LLU is looking increasingly like the silver bullet that never was (cf. Vodafone's recent decision to go BTW).
Maybe people are realising that PlusNet's prior market communications (About diversity of supply and providing a high QoS product) were the right strategy.
And yes - you can debate till the cows come home about whether they can actually deliver that strategy