Hi
Of course there is twisted pair and there is better twisted pair, as I understand it the BT normal stuff isn't twisted enough for the sort of frequencies pushed through it for ADSL/VDSL
It's all a hack for data over POTs. If you strip back telephone cable it isn't always obvious that it is twisted as the twists are far apart (okay for voice but not good enough for higher frequencies), whereas data cables like Cat 5, Cat 6 etc have many more twists per metre to better prevent crosstalk and interference.
Regards
Phil