Spinwing,
I suspect Mr S was trying a tad of sarcasm,
but:
1. ISTR spending a bit of time IMC in Bristow's 206 IFR trainer, but that was a long time ago so things may have changed
2. CASR 1988 175A,
here gives you the allowable Single Engine IFR rules for Australia:
175A Restriction on I.F.R. flights by single engine aircraft
(1) The pilot in command of a single engine aircraft must not fly the aircraft under the I.F.R. if the flight is not in one of the following operations:
(a) private operations;
(b) aerial work operations;
(c) charter operations that do not involve the carrying of passengers for hire or reward;
(d) charter or regular public transport operations that involve the carrying of passengers for hire or reward, if:
(i) the operator is approved in writing by CASA to conduct the operations; and
(ii) the operations are conducted in a turbine powered aeroplane approved in writing by CASA for those operations.
Penalty: 25 penalty units.
(2) CASA may issue directions to an operator to ensure that any of the following matters do not affect the safety of a regular public transport operation to which paragraph (1) (d) refers:
(a) seasonal influences;
(b) the conduct of operations by night;
(c) adverse weather patterns;
(d) the terrain below, or in the proximity of, the route used in the operation.