In my post on Brisbane's King George Square busway station, I emphasized that the service pattern was of few routes running at high frequencies. Michael Setty commented
What is really happening in Brisbane contradicts the marketing pitch made for so-called "Quickways" (grade-separated busways) by www.movesandiego.org, which emphasizes so-called "world best practices" focusing on the ability of buses to operate directly from origin to destination ...
Yes, Brisbane's busway is pretty much what the Move San Diego folks mean by a "Quickway." It's a fully separated road for buses only, which serves stations that have been built to a rail-transit level of amenity.
And yes, one virtue of busways is that buses can run along part of them, and then branch off to serve other areas directly. Rail transit obviously can't do this. When your rail transit journey has gone as far as the rails will take you, you have to connect to a bus or other mode to complete your trip.
But this argument for busways comes with a note of caution: Only during the peak period will there be enough demand to run direct busway buses to most suburban areas. If you live in a low-density suburb near but not on the busway, your area may indeed have some peak-period trips direct to downtown via the busway, but you're unlikely to have that service all-day, evening and weekend. During those times, you're most like to need to take a local bus service to a busway station and then connect to a busway service.
Outside the peak period, the best practice is to run few routes, so that they can be run frequently. The pattern is clearest in the Ottawa busway system (which did much to inspire Brisbane's).
As you can see on the map here, most parts of the Ottawa busway system have just two or three routes on them all day, for a total of eight "rapid transit" routes citywide. These all-day services are meant to be a frequent "rapid transit" experience*, but to support that frequency, they are targeted to high-ridership areas rather than spread out to serve every suburb. During the peak commute period, many more buses flow through the busway branching out to almost all the surrounding residential areas.
So yes, busways make it physically possible to run direct buses to every suburb. But outside the peak period, it may not be good planning to do so.
Conversely, when a busway is proposed for conversion to light rail, as in Ottawa, one of the political obstacles will be the need to sever all of the peak commuter express services that run through the busway but then spread out to serve every suburb. Light rail won't be able to spread out like that, so all these commuters will be forced to make a connection. This can be a good thing. It can even be faster for them. But it's not politically painless.
* subject to that busway's limitations, the biggest of which is its nonexistence through downtown.