as with most work related expenses provided you are employed in a field and you self educate then expenses relating directly to your chosen field can be taken from your taxable income.
In cunning's case, all he/she needs to do is be employed in the field to write it off as a legitimate expense. ie he/she while working for NJS prior to being employed by Jetstar pays Alteon for the endorsement costs then it is a legitimate expense even though he/she does not work with the intended company, yet.
There is enough information out there for anyone to research and form their own opinion, any accountant can access this, the AFAP have made information accessable to the cases that they have contested. If you are still not sure, get a private ruling from the tax department. In any case:
Be employed in the field and expenses relating to self education in that chosen field then it is OK. Fortunately an endorsement is self education.
my 50c worth