Regarding the multiple garbage trucks, there is at least the possibility of the truck having multiple separate containers to store different types of garbage.
This city also has 3 systems which require at least 2 different truck types just for mixed garbage.
(bags, underground container and bins)
Then there is the greens bin and the trucks for that.
The paper bin and the trucks for those.
And the plastics are picked up as bags or from a big collection container, so I guess thats 2 different trucks as well.
note: also there are big collection containers for paper and glass, which have different trucks as well.
This city also has 3 systems which require at least 2 different truck types just for mixed garbage. (bags, underground container and bins)
Then there is the greens bin and the trucks for that. The paper bin and the trucks for those. And the plastics are picked up as bags or from a big collection container, so I guess thats 2 different trucks as well.
note: also there are big collection containers for paper and glass, which have different trucks as well.