What determines an air conditioning compressor's location?
Usually it's not a big deal to move an AC compressor a bit. However, there are some common constraints to placement based on the mechanical performance of the system and local codes.


The compressor must have electrical power and control wiring. But wiring is easy, not typically a limiting factor.
You also need refrigerant lines. Manufacturers specify a limit on the distance and total height of these lines. You usually can't put a compressor many floors below the evaporator.
The compressor must be accessible for service. Modern codes usually require an electrical outlet nearby too.
The compressor must have adequate clearance from adjacent buildings, walls, decks, etc. to ensure good airflow.
You may be required to consider noise or setback requirements. Most towns don't want you to place a noisy compressor right on the edge of your neighbor's property.


I got to learn a bit about these rules when we had AC installed last year. My city electrical inspector required the compressor to be rotated in order to place the electrical access panel on a corner not adjacent to the house. (As far as I can tell this is ridiculous and uncommon even in our city.) The installer had to have both their refrigerant tech and electrician out again to rotate the unit. So it's a bit of a pain, but it's certainly doable and if the only reason they didn't put it in the place they previously agreed to is forgetfulness/laziness then you should demand they fix it.