I did make some further enquiries about this, but it seems that BTw are giving little information away about it.
Each week they are releasing a list of PEWs to the ISPs, but atm its nigh on impossible finding out any info exactly what work they are doing - although its thought it may be a first step towards 21C... but that is speculation.
All the lists say are the exchanges and which dslam the work is to be carried out on.