"I should add my source was very reliable and I only want to verify - and to see if anybody else knows about the virtual 'margin call' clause in the Australian mortgage contracts?"
I read my entire mortgage contract when i bought my first home and i think it had much worse clauses than just margin calls
in fact I recall seeing John Howard on TV say australian mortgage contracts had some very harsh conditions in them and something needed to be done about them
considering the debacles that have happened in the US why would anyone assume otherwise?