> wouldn't it be simpler to make it a "Internet not delivered by NBN tax" tax.
Simpler maybe but politically unpalatable. It makes it impossible to not look like your trying to ruin a business model. To be honest, I'd rather they funded it from general revenue. It is useful infrastructure with a long shelf life* and will add to GDP and hence future revenues, plus borrowing is still at an excellent rate.
*FTTP, not the crappy FTTN half arsed obsolete before it's finished crap.
> would assume this pretty much impacts every mobile phone (cell phone for our American readers) bill too.
No. It won't impact mobile. From the linked proposal:
"... which will require all eligible fixed-line superfast broadband networks to make a proportionate contribution to the long-term cost of these services"
4G isn't fixed line.