I have read in a previous post that there can be brush fires in the Blue Mountains in hot weather. Would a daytrip (bus tour) to the Blue Mountains in January be ill-advised?

No- you will be safe on any bus tour. The fires do not put tourists in danger as far as I know...

You might be surprised to know that many people live in the townships of Blue Mtns and regularly commute to Sydney for work. I wouldn't worry.

Bushfires (not brushfires) do break out, but the Blue Mountains is a vast area and human settlement is confined mainly to a string of dormitory suburbs populating the ridgetops following the highway and rail line. The rest, by and large, is a massive swathe of unpopulated wilderness.

To have these settled areas threatened to the point that highway traffic were closed or the tourist areas in an around Katoomba off-limits is most unlikely. I would not be concerned in the slightest.

(I lived in the BM for 7 years.)

Thank you all for your kind responses. We travel often and truly appreciate the insider information we glean from these travel boards.