Utilities placements and garbage

Services that can be placed anywhere in the city as long as there is a road attached between them and the residences:
- Power
- Water
- Waste Management
- Sewage

Services/specialisations that your residences have to be within the zone of for them to take effect:
- Fire
- Health
- Police
- Parks
- Education
- Transport
- Gambling
- Landmarks
- Entertainment

So to answer your question, anything in the first list above can be placed where you want in your city and still service all the residences - they serve a set number of buildings rather than a specific zone. Just make sure that you have an adequate number of service buildings corresponding to the number of residences (e.g. for water, 50 residences will require at least 6 basic water towers or 1 water pumping station). Also ensure that if the service has a dirty radius - indicated by a brown patch when selecting the service building - it falls outside of the residences' zone or they'll complain about the smell. I personally have all my power, water, waste management and sewage buildings all located on the top row of the map away from all my residences.

The total size of the SCBI city map is 100 squares x 100 squares. If you go for the maximum buildings for each emergency service - the hospital, police precinct and deluxe fire station - you'll find that you should need 4 of each for the police precinct and the hospital. The problem one is the deluxe fire station which has a smaller radius (22 squares x 22 squares) than the other two emergency service buildings for some reason. The placement of the fire stations can leave gaps in coverage if you have 4 like you do with the other two emergency service buildings. You can either have a gap in coverage and place other buildings/specialisations in these gaps or buy small/basic fire stations to fill in the gap in coverage.

At least that's my experience with the game.