If you hold stocks traded on a US exchange in US$ (or other foreign property), even in an account at a Canadian institution, you must file a T1135 (by regular mail or fax - no e-filing for that form yet) if the aggregate total Adjusted Cost Basis exceeds $100,000. CDN at any point during the tax year, regardless of what type of account (TFSA, RRSP, etc). Penalties can be severe if you fail to file the T1135.
For this reason alone, it might make sense for POET to maintain at least one robust and liquid Canadian listing, in addition to Frankfurt, Nasdaq or wherever, so that Canadian investors can continue to own POET without worrying about the foreign property reporting requirements.
http://www.cra-arc.gc.ca/E/pbg/tf/t1135/README.html
