ACCC will be concerned from a domestic mobile network operator perspective (MNO).
Pacific Internet was sub cables not even landing in Australia IIRC.
I dont think they will be concerned about concentration of fixed line, as VHA are pretty insignificant and the NBN creates a level playing field at a retail level.
ACCC wont be bullied or dictated to though, its their job to stick up for consumers, not corporations. They do need to ensure their decisions allow for a reasonable return on investment though, and I suspect ACCC will let it go ahead though because of that and that MVNO's provide extra competition that wasnt there years ago when they did have serious concerns.
