I have heard an argument that seperating the plastic (seperate garbage truck once a week) is actually worse for the environment and costs more.
But local governments think of it as a huge succes because they only measure how much is seperated in the new proces, not how it compares in all aspects.
The reason it costs more is because workers still have to seperate plastics from other types of plastic.
Also the garbage truck every week, which is also the reason for more pollution.
Plus all in all, the seperating plastics makes people moraly satisfied ( "they did their part, now back to buying more shit" ).
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.
The reason it costs more is because workers still have to seperate plastics from other types of plastic. Also the garbage truck every week, which is also the reason for more pollution.
Plus all in all, the seperating plastics makes people moraly satisfied ( "they did their part, now back to buying more shit" ).