Yes, but most of these system aren't internal, they're going half way around the planet to somewhere that it's cheap to employ the call centre staff.
You're info is probably more current than anything I know, but I do know I've had some truly god awful audio links to tech support in the Indian sub-continent, and there were some clear compression artefacts. Calling back later you can get tolerable quality, which suggests to me that when the lines are busy the system has started doing something like bit stealing, with it's consequent quality losses.