Yes you can still take out a policy with Police Health, but you will need to serve a 12 month waiting period for pre-exisiting conditions. This does not apply for psychiatric care, rehabilitation or palliative care.
A pre-existing condition is one where signs or symptoms of your ailment, illness or condition existed at any time during the six months preceding the day on which you purchased your insurance or upgraded to a higher level of cover.
A medical practitioner appointed by Police Health (not your own doctor) is the only person authorised to decide that a condition is pre-existing. The practitioner must, however, consider any information regarding signs and symptoms provided by your own treating doctor or specialist.
Further information on waiting periods for pre-existing conditions