It all depends how well the paint has adhered to the surface and how sound the surface is. You might want to lightly sand the paint to give it a key, then repaint over the top.
Best way to get paper of is too use hot water with vinegar mixed in, score the paper surface or use a 'papertiger'...
Nowadays there is no requirement for the cables to be capped with that plastic rubbish, as long as it's installed in the areas set out by the recent building regs. So you can have the cables clipped to the wall with cable clips which obviously allows plaster better adhesion to the wall.
In...
In general if the lining paper is well hung (no pun intended) you'd need little filling. Though I do use filler where absolutely necessary to ensure the best finish possible.
Lately I have been using the non-woven papers which apply much easier and quicker and don't tend to shrink. So you get...