I was just looking at that section of the tech manual yesterday. I was pondering the thickness of a starfleet hull wrt to model I was making (~1 foot/0.3 meters).
Anyway, as I understand what the manual was saying, AG is generated by superconducting spinning disks. The effect generated moment to moment falls off rapidly, meaning the grav field has a range of about 30 meters.
The system doesn't require much power and continues to operate even if it has no power for up to 240 minutes.
Because it has an effect beyond 1 deck one must assume that every deck is not equipped with it's own gravity generation system.
Beyond that everything said by Mysterion is true according to the tech manual. The DS9 Tech manual indicated, however that Cardassians (At least wrt to DS9/Terok Nor) don't do it that way. They use mats of tiny grave generators and it is implied these are installed on every deck. This scheme would be more suitable to the idea suggested here as the gravity field fall off must be limited deck by deck. Cardassian generators also remain active even if unpowered but they dissipate their graviton generation in 48 minutes. However, they seem to do this with stored plasma rather than inerita, so it is possible to draw power from the grav mats and transfer it to other applications, suggesting that the gravity could be maintained for longer than the stated 48 minutes by effectively transferring gravity from other parts of the station.