Can someone answer a question about Ubuntu touch?

I'm a bit late to this thread. Both my n900's died. I ordered a pandora, and likely will order a pyra.

Linux on android isn't really appealing to me since I can't really modify how the underlying android device behaves.

I was reading about the bq M10 this morning and I saw this:

"Traditional Xorg-based software runs on the tablet in a confined, secure container using Xmir."
http://www.omgubuntu.co.uk/2016/02/b...u-need-to-know

Does that mean that Xorg-based software is sandboxed and cannot open critical system files read-write so I can modify the device's behavior?