BT supplied the graph on this article:
At the time, we didn't know what the technology behind options 1 and 2 were.
Now, almost a year later, we know that the technology is
- Using the VDSL2 8b profile, which allows a higher aggregate transmit power of 20.5dBm (instead of 14.5dBm), but only over 8.5MHz
- Setting the cabinet's PSD mask to allow maximum power throughout the spectrum (instead of restricting it for ADSL compatibility)
- Adding vectoring
We still don't know whether this technology is option 1, 2 or something else. My best guess would be option 1.