When I have a region cluster of 4 cities in SimCity, I logically start out by building one city, and then move on to build other cities in the cluster.
I move back and forth between my cities to gradually improve and perfect them.
In one of my cities, which is based on tourism, I have a massive cash flow and can therefore import materials needed to my great project - in this case, the Habitat.
This city will deliver the imported materials to the great project, along side the materials gathered from the recycling station (metals in the case).
If I go to one of my other cities, will the city mentioned above keep delivering materials to my great project?