I discovered a nice tool, U-Verse Realtime, which lets you show many parameters of your Uverse operation. It's free software for Windows machines, and it seems to work in my virtual Windows XP machine. (VMware under Ubuntu Linux.)
The first bit of science is to measure my "bitloading". That shows what parts of the frequency spectrum are being used for the underlying DSL connection. The results:
The increasing line attenuation with frequency is apparent. (At least, if you believe that "bitload" has something to do with signal power. I don't really know that.) The electrically measured line length from the Uverse node is 2554 feet, which puts me in the lowest of 3 service tiers.
OK, second science test. The active DSL spectrum includes the 80 and 160 M ham bands. What's the interference potential? This is not a simple question. The interference from Uverse's DSL connection might not be much of a problem. Why? The received signal is going to be weak (indicated line attenuation is 21.6 dB.) The locally stronger transmitted signal, 3.7 - 5.0 MHz, is mostly outside the 80 M band, although there could be problems between 3.7 and 4.0 MHz, in the SSB band. Fortunately (?), the 80 M band is naturally so noisy that the interference might not be noticeable.
The thing to worry about, I think, is interference to Uverse service. I ran a very short test at ~3536 kHz CW. I was downloading a large file over the Internet and listening to an HDTV program in the other room. Transmitting with ~90 W output caused no apparent problems. Transmitting at ~850 W killed the DSL connection pretty quickly. Download stopped, and the TV image froze. It took about 70 seconds to reacquire the signal after transmission stopped. (At least nothing was destroyed!)
This is all very preliminary. We will need to improve the wiring and experiment with ferrite chokes -- probably on the incoming DSL connection. There is no guarantee that kilowatt 80/160 M operation will ever work, but it might...