2 years later and it's still clear as mud. From the CASA web page.
Class 1 medical certificate
You need a Class 1 medical certificate for these licences:
- Air Transport Pilot Licence
- Commercial Pilot Licence (other than balloons)
- Multi-crew Pilot (aeroplane) Licence
- Flight Engineer Licence
- Student Flight Engineer Licence.
So for a Cessna Citation 500 which i s a 2 pilot aeroplane (5400 kg aprox) you need a Multi-crew pilot licence. According to the CASA infor to hold a multi-crew pilot licence you need a Class 1 medical.
What if you have a Citaion 1SP which is a modification. As long as certain equipment is servicable you can fly it single pilot on a class 2 medical. if that equipmet is US it reverts back to its original certification requirements as a 2 pilot aeroplane (MCP licence Class 1 medical now required).
Additionaly CAS no longer mentions anything abut exercising the privilages in a commercial operation. So it seems now there is no difference betwee commercial and private ops.
or...have I got it all backwards?