I agree with a garage being located in both places but approach my industry placement a little differently.
Instead of placing my industries downtown, I place them close to the raw material areas instead. This allows the teamsters to walk from the farms and logging camps to the nearby factories instead of hauling the products back to the downtown area and clogging up downtown with trucks arriving with raw materials and leaving with finished products. Since a garage is nearby for the farms, teamsters will also use the garage to haul finished factory products to the docks instead of walking to the docks and the factory workers will use the garage when it's time to go home. (It also helps keep pollution out of the downtown area)
I reserve the downtown area for housing, garages and service plazas (hospitals, churches, resteraunts, marketplaces, etc.). When housing is close to a service plaza people will more likely walk there rather than drive. This also decreases traffic flow. The diplomatic minstry goes right next to the palace so El President can stop by one every six months to improve diplomatic relations with the superpowers. (And to get some CocaCola and Havana cigars from the ambassadors.
Buildings like armories, immigration office, police stations etc have their own garages and can be placed as needed outside the downtown area. I usually place any additional construction office and teamster offices scattered evenly over the island. This helps speed up the contruction workers getting to a nearby bulding project eliminating some of the wait time for them to start building something.
Once the downtown area is completed, the downtown Teamster office and Construction office is closed to make room for better housing or improved service buildings. Nothing on my island is fixed in stone - except for El Presidente's Palace. My people insist it remains there - just a stone's throw away for the nearest protester.
It works for me but may not be your style of play.