Well said Tarman.
PDG have a large fleet of helicopters, their own engineering, quality control, safety management etc. This all costs money, not to mention the CAA charges to boot. Everything has to be protected and if this means closely watching the one man bands/smaller operators that offer a better price then surely thats an acceptable practice? Surely thats acceptable to report potential misdemeanors/illegal public transport - especially if you're bending over backwards to do something by the book when others might not be - afterall short-cuts can be dangerous.
At the end of the day, in this scenario, it was found the other operator wasn't doing anything wrong. At least now they know that operating incorrectly should not an option and they should continue to do things by the book.
The 'paid photographer' was more than likely PDG staff (i'll put a wager on it) - sounds like a sensible use of resources to ensure fair and honest competition.