Your subject doesn't seem to match the question....
And I think that you're confusing TV tuners and an AV line in: a TV tuners allows you to pickup broadcast signals (BBC1, BBC2, ITV, Ch4 and C5) and a Freeview TV Tuner will pickup the Digital equivalent (BBC1, ITV, etc and also TMC, Sky News, Sky Sports News, ITV2, 3, 4, etc, etc)... NEITHER of these is required if you're just trying to setup a reversing camera as these will generate their own AV signal wich jsut needs to be wired into the head unit.
To answer the subject and first part fo teh question: I know that the RNS-E with a CD stacker and iPod cable is an Audi supported config, so there should be no problems there and you can add in a Freeview TV tuner to that setup and use the "TV" channels for that.
I'm not sure how people have done with setting up reversing cameras AND Freeview TV tuners, but I'm pretty sure that people have setup TV tuners and Playstations before, so presumably there are enough AV lines in on an RNS-E, so I think you'll be okay.
If the question is relating to an Alpine head unit rather than the RNS-E, then there's no point in asking the RNS-E question as you'll be putting the Alpine head unit in INSTEAD of the RNS-E - just look at the head unit's manual.