It sounds like it is the standard Ubuntu userland, but I am not sure if that is a guarantee for root access. If most of Ubuntu is still under GPLv2 (or other non DRM restricting licenses), then there is nothing stopping the manufactoring from locking down the phone. If enough of Ubuntu is under GPLv3, then I think that the manufacturer would need to replace those pieces in order to lock down the phone.
Just because you use software doesn't mean that the restrictions on the software apply to software it runs. It's only when you re-distribute or modify GPL software that the GPL licences kicks in.
