Not all of the oil companies are OGP compliant (yet). So if an operator has a contract with a non-OGP customer, it is still possible to be hired with <500hrs.
Anyway, 500hrs TT is bit of a red herring. IIRC, the OGP requirement for a P2 is 500hrs ME heli (or having trained in an establishment with a recognised course of training, or words to that effect. Which is why Bristow Acadamy is often cited).