Sorry I should rephrase that. I don't know a single EMS operator that the aircraft/crew doesn't have the ability to operate IFR.
Depending one which base/client you are flying for then there's either nitesun or NVD for operations below LSALT at night (you still have to be visual at LSALT prior to descending).
Operations below LSALT will vary from one operator to another, as coyote points out it depends on what's in your ops manual and what exemptions CASA has approved.