Notwithstanding the new wording of Article 7 of the OECD Model Convention and the OECD commentary thereon, CRA continues to consider (in light of Cudd Pressure and s. 4(b) of the Income Tax Conventions Interpretations Act) that notional expenses are not deductible in computing the profits attributable to a Canadian permanent establishment for Treaty purposes – with the exception of PEs of qualifying U.S. residents, as to which there is an agreement with the U.S. competent authority which overrides s. 4(b) of the ITCIA.
Neal Armstrong. Summary of 26 May 2016 IFA Roundtable, Q. 2 under Treaties – Art. 7.