It just occurred to me, why not a pedestrian tunnel network so that people can still walk but do so out of weather (hot or wet, or cold!)?

Sydney has an extensive system of these.

No need to extend rail network, just make it easier for people to get to the (existing) station system??

You're missing the point! The point of CRR is to create additional capacity to the existing QueenslandRail city network.

Without it, there can be no new lines built, no extra trains, and no extra passengers.

-"Worse news is that the numbers of patrons are falling - from 60.7 million to 57 million in a year."
As the article says, Translink measures in a different way now. Previously they would get people to manually count vehicle loadings, but now they measure by Go Card Touch on/offs...In other words, previous years would have been overestimated, hence the statistical decline.

"With the exception of the new line to Springfield, there are no new lines being laid and no new stations proposed."
None proposed? What about CAMCOS? Extension to Cooloongatta? Redcliffe? (Yes, it's back on the planning documents!)

Anyway, this article seems to be missing the point as to what Cross River Rail is for. Its not so CBD workers can have 'convenient' new stations. Its because there isn't enough CBD track capacity.

In total there are 19 'tracks' in the Brisbane network (4 from Caboolture & the North/Sunshine Coast, 2 to Shorncliffe, 1 to Doomben, 1 to the Airport, 2 to Cleveland, 3 to Beenleigh/Gold Coast, 4 to Ipswich/Springfield, 2 to Ferny Grove. These 19 tracks have to merge into 4 to get through the current CBD tunnels, and the 5 tracks from the southside have to merge into 2 to cross the Merivale Bridge.

Current services are already overcrowded, and the CBD infrastructure is nearly at its limit in terms of trains per hour it can take through. If more frequent services are to be scheduled, and new lines to be built then the CBD capacity constraint needs to be addressed. Notice how the new tunnel will begin before the Cleveland line junction, and finish after the Ferny Grove junction? This bypasses all the current bottlenecks....The new underground stations in the CBD are just a bonus since they are 'on the way'.

"An additional handbrake on increasing patronage of the heavy rail network is that even getting to a suburban train station in order to catch the train isn’t easy. If you live more than a kilometre from a train station (which means the overwhelmingly majority of all residents) you would need to drive your car to a station"
At many stations buses are timetabled to meet trains as they arrive. Admittedly they need to do this better, but there's your number one option.
I'd say the main reason patronage isn't higher is because Brisbane still runs with an archaic 30 minute off peak frequency, when 15 minutes is the norm in Perth, Melbourne and Sydney. Fix this and suddenly the network becomes much more attractive to 'turn up and go' passengers.

"What public transport alternatives are available, and how do those costs compare? (The bus system relies on a lower passenger subsidy than rail, plus largely uses existing road infrastructure and routes can be expanded largely without the sort of investment required of rail. What would even a $1 billion investment in the bus system do, by comparison?)"
$1 Billion would get you a bit over 2km of busway...(The current first stage of the Eastern Busway is costing $465.8 for 1.05km)

"The latest government figures show that every trip, by each and every commuter on the City Train network, is now subsidised to the tune of $10. That’s per trip, so for every daily return trip, the taxpayer is forking out more than $20 per commuter. And that’s after commuters have paid their fare - remember it’s only the subsidy."
And what if the train network wasn't there? You'd be stuck because taxpayer money would have to be spent on other forms of transport to meet the same demand (Dont forget that rail has the highest carrying capacity of all urban transport modes, a railway can move 30,000 persons per track...a 4 lane freeway 7200 cars per hour per direction.