Mmmmmm ...
Sounds like Melbourne..... be careful very careful.
Obviously the METARs and TAFS become important... you cannot fly in known Icing so ... if you cannot go VFR think about not going ...no shame attached.
Unlike an aeroplane you will not have anti-icing available so thinking you can climb above a freezing level and be safe is not healthy .... and remember you might have to descend thru the icing to recover ....
If the job is Melbourne and the a/c is a 412 OEI ops might mean depending on the situ you might NOT be able to maintain OEI flt at 5900' anyway.
I am sure your Chief Pilot will have the official company requirements for the task.