Both Series 1 and Series 2 came standard with the Supercharged V6.
The naturally aspirated V6 was optional. Despite this there are quite a few naturally aspirated V6 Calais out there.
A P plater can drive either Series 1 or Series 2 but only if it's the naturally aspirated V6.
Your mate has to apply for an exemption with vicroads to drive a supercharged V6. The super6 fits in vicroads guidelines for an exemption (100-125Kw/tonne, family/passenger vehicle). But they review the applications on a case-by-case basis, 99% of the time they will pretty much just be like... Supercharged commodore, how about no!
More info here:
Lower perfomance turbo or supercharged vehicles : VicRoads