The U-Verse upstream data is sent in channels between 3.77 and 5.03 MHz on my system. The channel usage may be seen in the VDSL Monitor DMT Chart screen:
Using the QS1R receiver with a 5" square current loop sensor, I could detect the upstream signal by laying one side of the loop along the RG-6 cable. The following SDRMAXII display shows the upstream spectrum as an instantaneous spectrum and as a waterfall chart that shows periods with the probe on the cable and off about 10 cm.
Note that the gaps in frequency channel bit loading are clearly visible in the actual measured spectrum.
The upstream spectrum overlaps the top end of the 80 M amateur band (3.77 - 4.0 MHz), however the signal is weak and has very low spectral power density, making it unlikely to be noticeable in normal amateur operations. That is, unless there are gross wiring problems inside or outside the house.