I've recently been researching the Ubuntu Touch operating system and have stumbled upon answers to all your questions.
"does ubuntu touch work yet with CDMA?"
Well this is an interesting question that I was wondering myself as I am a Verizon user and the answer is quite simply, No. On a post by Ricardo Salveti, Tony Espy who is an employee at the company which owns Ubuntu made a comment in which he stated,
There is currently no support for CDMA devices in Touch, and it's not
on our current roadmap.
That said merge proposals are always welcome if someone in the
community wants to take this on...
This shooting down our hopes, yet the post this comment was upon detailed how to enable 3G data, but the method may not work on CDMA. (I will test this myself when I get a Galaxy Nexus using CDMA code named toro)
updates from terminal
I have found that currently there is a way to updating without reflashing. On the wikipedia page for Ubuntu Touch, there is a field labeled Update method which reads "Click Update Manager, Image Based Updates" and I have found that others say command line works just as well.
You must understand that the Galaxy Nexus and Nexus 4 are two different devices. Neither of which have an SD card slot.
The Ubuntu Touch operating system is a full operating system with a codebase similar to Ubuntu which means the Debian APT system is implemented, yet it is not identical as it does not use Xorg and runs on an ARM processor. These facts as well as the launchpad page for python3 show that it is available on the mobile operating system.
The Nexus 4 code named mako only shipped with GSM compatibility. The Galaxy Nexus is sold for both GSM and CDMA. The Galaxy Nexus for CDMA was code named toro for Verizon and toroplus for Sprint. Yet Ubuntu Touch is said to be released in April of 2014, this year. This fact gives me hope that CDMA support may be developed in the coming months.
This question was answered for the purpose of those researching Ubuntu Touch OS and Serves not for helping you chose what to buy seeing as its been so ling since you posted this, but as a reference.
How to update my already installed Ubuntu Touch image?