It`s too bad there are no Good Bus models available,as they share many truck parts such as Engines and Axles
I drive a transit bus in Los Angeles and I also own a 1975 Flxible Transit Bus from Sacremento that I have preserved as it ran in service.
Transit buses pretty much used GM 6v92 or 8V71 engines until recently
Now they are pretty much powered by inline engines Either Cummins L10 or Detroit Diesel Series 50
Transmissions used to be "V" drive with the engine sitting sideways and then the transmission forming a "V" driveline
Our buses now are "T" drive with the Engine "Front" directly at the rear and Coupled to an Allison "World 600" transmission
Axles are usually designed by Rockwell,with air brakes
I always wished for a GM "Fishbowl" odel or a Flxible "New Look" model but nothing ever transpired
it`s true that there are some bus banks out available but are usually very toylike
Only Corgi (That now of) Really ventured into making Transit Bus Replicas
NABI us industries came out with a promotional bus for Santa Monica Municipal Bus Lines That was Very Realistic and was available at their main office but beleive they sold out of them
We could only hope that someday we might see something
Thanks
Phil