Up until 6mths ago i was living in Bunbinla Ave and had been for 2 years, i did a fair bit of exploring of the local area. I wouldnt really surgest that the route youve mentioned really exists too well these days. You may find it possible to bush bash your way down, but most tracks have been 'regenerated' lately.
Another peice of advice; if you bike can handle the decent down to Emu, would you really want to ride it the rest of the way to nepean? Personally i'd recomend a cheap roadie or MTB+Slicks for the commute. You can Mix it up between Old Bathurst road and Mitchells Pass for the decent both are fun.
If you'd like to meet a few locals for a ride you can PM us or head here: bmorc.com
Cheers, Rory.