Ok all new article on the register:
http://www.theregister.co.uk/2008/04/14/bt_phorm_2007/
".....Today Phorm said the 2007 trial was actually performed on "tens of thousands" of lines. It refused to provide a specific figure, but at the absolute least there are 38,000 BT Retail customers unaware their communications have been allegedly criminally intercepted in the last two years. The number could be as high as 108,000."