On my line its taking at least 15mbit attainable sync off.
I've never tried working that out for my line...
Apart from the cutback, my maximum bit-loading is 13 over a very wide plateau (tone 65 through to 535). The cutback dip is from tone 90 through to 375, and drops down to 4 bits, making (almost) a nice triangle.
I make it that it has lost around 1,300 bits because of power cutback, which I reckon to be worth just over 5Mbps.
As a cross-check, I reckon I can fit 16 triangles of that size over the downstream bit-loading graph, and 1/16th of 80Mbps is indeed 5Mbps.
The shape of my cutback matches the diagram in part B of the ANFP, for the line labelled "CAL=30". That happens to be the middle level of the CAL values.
Most theoretical speed-distance graphs suggest that you'd get around 15Mbps at 2km; I'd guess that ADSL2+ would lose an identical amount of speed if it were sourced from my cab, so the top speed here would be likely to be around 10Mbps.