The jobs in Antarctica are sometimes advertised on an internal job posting but the turnover is low. Helicfii is incorrect, PHI International operations do not operate separately from the rest of PHI and come under the authority of the Chief Pilot and the Director of Operations.
The contact details for the Manager of International is on the PHI website and while he will have some input as to who is hired, there will be no escape from the normal HR interviews and processes to being hired by PHI.
Although international operations are traditionally fed from applicants in the GOM, it is not beyond possibility with the current shortages that a more direct entry into international if not Antarctica may be possible.