The litmus test for RPT is if it is "available to the public generally".
As said above there are operators who have advertised fixed schedules to fixed terminals, which are NOT RPT as they are not available to the public generally. (ie you need the mine's security clearance)
As long as someone is paying for the whole flight and cannot walk off the street and buy a seat it is not RPT. If it's the same blokes every day, then they have no case to answer.
What gets me though is how can a so called charter "broker" can advertise aircraft that he doesn't own or have an AOC for? There's one particular one who implies that he has every frickin' aeroplane in the country when all his AOC is approved for is PA-31's!!