The response i got from the ministry of finance with respect to US filing issues was reassuring if for no other reason than it appears to put a saftey net under all dual-cdn-us citizens resident in canada in the event that the IRS decides to become too punative.
the two key quotes were
"...penalties imposed by the IRS under FBAR will not be collected by the Canada Revenue Agency (CRA) on their behalf. While the Canada-US Income Tax convention contains a provision that allows for the collection by a country of taxes imposed by the other country, this does not apply to penalties imposed under laws that impose only a reporting requirement."
"Furthermore, the CRA does not and will not collect the U.S. tax liability of a Canadian citizen if the individual was a Canadian citizen at the time the liability arose (whether or not the individual was also a US citizen at the time)"
http://www.denisesavoie.ca/download/155 ... aherty.pdf
fyi - Response from canadian ministry of finance
Moderator: Mark T Serbinski CA CPA