how can existing mgo shareholders trade , page-4

That is a good question... up until you asked it I was expecting MGO with title Marengo Mining CDI, but just had a look at the "booklet" and couldn't see it mentioned anywhere. Might end up being MRN to match Canadian symbol. It all happens automatically in CHESS, I have always had the intention of holding... doesn't really matter.

Also be aware of the tax implications, you have the option as a ordinary Australian retail investor (if you like me) to seek rollover relief from CGT if the shares are held at a profit at the time of exchange or crystalise a profit or loss ....

Booklet for more info. It is like a bible in size

http://www.asx.com.au/asxpdf/20121031/pdf/429txpr8kb8mhb.pdf

Other later ASX announcements may help... much shorter. :-)