so is there a way to prevent routing through, say, *.att.net?

I expect though that it's done at a level outside of the control of an individual pc.
(done at the ISP level perhaps?)

It's likely that if your ISP isn't ATT and the endpoint you're contacting isn't ATT, that none of you're traffic will pass through their network.

But if you're paranoid, and you should be, strong encryption is your best bet.

They would have a hell of a time decrypting the comings and goings of my packets,which happens to be many many gigs a day.

If you want to output your tracert to a .txt file just do it like this.

tracert 'domain' > tracert.txt


Thats how I always jew my provider for discounts of my monthly bill if I notice something awry.I save it to a text file and email it to them. :/