Indeed, one can have less or more complete UNIX environment in the Ubuntu Touch device. Direct use of the “apt-get” is not recommended as the filesystem is purposely made read-only. But it is possible set up and to use chroot environment and the have a separate system for the tools.
A nice guide is here.
There are limitations, of course. You have a separate space with no link from inside to outside and there is no (simple) way to use GUI or graphical applications. But most of CLI stuff works well (the Octave, the GCC, the Lynx and the Links, the Vim and so on).