The alignment is no narrower because you need an access road alongside the busway so that emergency services and breakdown repair vehicles can access.
Why?
A breakdown repair vehicle will be owned by the bus operator and thus can be expected to be fitted to travel on it.
And how often do emergency services need to get to a bus between access points?
The busways in Leigh and Cambridge have a cyclepath beside them it is true that can be used for vehicels as required.
But they are normally used for people to walk and ride bikes on them.
A public transport road with separate cycle/footpaths is going to be even wider than this, and cyclists are going to nervous about sharing a road with lots of fast moving buses so will likely insist on a separate cycleway.
And thats before the uber/taxi lobby manage to gain access to a "public transport" road and clog it up.
EDIT:
Worth noting that the O-Bahn in Melbourne certainly doesn't have an access road.
Don't hold back. Tell us!
In many "safety case" and similar fields, especially in my own field of nuclear related stuff, we have had serious problems with contracted designers at engineering firms acting in a manner which whilst in their own best interest, was certianly not in the contractee's best interest.
Spending far too long chasing minor optimisations in materials use or whatever but running up costs far in excess of the savings.
Or even chosing design solutions that guarantee future work (hence the enormous proliferation of 'interim' solutions)
Most of the time on the railway or other fields we are not pushing the limits of materials, so the current way engineering work is done is not particularly helpful. And the regulation doesn't help this either.
But that is going drastically off topic.