Civil Aviation Notification Procedure (CANP)
In UK, powerline survey, sporting activities, aerial photography, crop spraying, underslung loads and anything else low level (i.e. below 1000 feet) that will affect military operations should be notified on 0800 515544. The relevant (RAF and ATC) authorities will informed by the duty airman of the details. Naturally, try to give them as much notice as possible.

Pipeline Survey
This is similar to Line Patrol, so most of what is said there will apply here. Gas pipelines (or whatever) are not very far below the surface of the ground, and potential hazards include building works, ditch construction, drainage, flooding, leakage and falling trees.
1/250,000 scale maps will be provided, on which the pipeline route should be marked, though it will be obvious when it’s just been laid. Observers will be using larger scale maps supplied by their companies. The normal patrol height is 300 feet (in UK, anyway), with an associated speed of 50-80 kts, taking into account the efficiency of inspection, terrain, wind direction and practical helicopter operation (avoid curves, etc.). However, between 500-700 is recommended to avoid low flying military aircraft. You should not approach closer than 300 feet to any person, vessel, or structure, and only closer than 500 feet within a horizontal distance of 300 feet from the pipelines.
The cloudbase must be at least 200 feet above inspection height, with a minimum visibility of 1500 feet.

UK Police Operations
A police force will either own its own aircraft or charter from operators as and when required, in which case the only things you can get away with are low flying (closer than 500 feet, etc) and going in bad weather. Even then, you can’t get closer than 50 feet, or 1.5 rotor diameters, whichever is greater. In fact, to take full advantage of any restrictions, your passenger needs to be either a police officer, an employee of the police authority, a medical attendant, a pilot under training, an Inspector, a Fire Officer, a Customs Officer on a joint operation, or any other agreed in writing by the authorities. However, there will always be a police observer, and the job involves a lot of cross-controlling when on observation, not to mention short-notice tasking.

As they may need to recover their costs from time to time, they may also need a Police AOC and Ops Manual (PAOM), though this depends on the country.
Prisoners
A prisoner is a passenger and qualifies for the normal safety considerations, although their movement is definitely not routine. Handcuffing should always be done to the front, so seat belts can be released in emergencies.
Potentially violent prisoners should be carried one at a time and have enough escorts to restrain them. In any case, at least two should be used, ensuring that neither the pilot, the controls or the exits can be reached.