Hi Les
OK, 60 year old single Mum lumbered with Condition 8503. Assuming that both children have lived in Oz for long enough to have become properly "settled", the first one to get
PR can sponsor Mum for an offshore CPV 143 or 173.
Mum will have to be outside Australia at the time when the CPV 143 application is lodged with DIAC and it will not be a valid application unless it is sent to the Parents Visa Centre which as you know is in Perth.
If the sc 676 is valid for multiple entry, Mum could go to somewhere like Fiji for a couple of weeks whilst the CPV application is delivered to the PVC by a reliable courier. Then she could return to Oz till March 2010, when she must leave because the sc 676 will expire.
Common sense suggests waiting till Mum has had to leave Oz anyway in March 2010 and applying for the CPV whilst she is outside Oz. She can then apply for another sc 676 but she should NOT rely on the notion that Condition 8503 will not be imposed on the new sc 676. It might be imposed and if it is there is nothing that Mum will be able to do about it except live with it.
This is a case where Mum might have been better off getting a Student Visa two years ago. Sure that would have involved tuition fees at International rates at least for a while but teh TAFEs are sometimes generous in this situation. A Student visa would have enabled Mum to work part time as well, to defray and probably pay the tuition fees in full.
She cannot switch to a Student visa at this stage because Condition 8503 will prevent it. I would say it won't be worth getting a student visa instead of a sc 676 at this stage or from here onwards because much of the wait for a CPV is now over anyway.
Cheers
Gill