We also had a discussion about how it would affect crosstalk and what PSD masks and PBO would be put in place depending upon the different 'E' side cab lengths. Obviously the further the cab is from the exchange then the more PBO has to be applied to protect existing adsl2+ lines.
I remember looking at the SIN, and the line profiles it suggested using for different test cases. If you assume that the line profiles used in the test give a hint at the expected outcome, then (IIRC) I think that the middle-E-side-distance cabs got worse performance out of the PSD masks than either the short-E-side cabs or the long-E-side cabs.
The trick is that the power has to be backed off more for longer E-sides, but for a smaller segment of the spectrum.
I have ask my isp about it .
Pretty much everything written about the concept comes from the SIN - which only includes test specifications for modems. There has been no public hint whatsoever of a product that makes use of such modems. anyone you could take to at an ISP would know nothing.
It might make sense as a product, but only as a way for BT to meet some of their USC commitments in the BDUK contracts. That would, perhaps, limit it to maybe 2%of premises.
I could equally imagine that vectored VDSL2 could be an alternative, though some people think it is only worthwhile up to 1km.