Can I claim to have completed my degree on my résumé, prior to convocating and receiving the physical diploma?

You can use the formulation

Degree to be conferred MM/YYYY

to indicate that you have passed all degree requirements, but are waiting for the degree to be officially awarded. This occurs fairly frequently, particularly for PhD students, who may finish at any time of the year, especially if their university only confers degrees once per year.

Ask your institution to give you some sort of confirmation to passed all the requirements for the degree. I don’t know about Canada, but at least in Germany such confirmations are the default¹ because all public institutions (and most companies) will require this for any employment or graduate programme requiring such a degree. Even if this is not a thing in Canada, your institution should be capable of doing this for people who intend to go abroad.

Use the wording from this confirmation.

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^{¹ But then, while most universities in Germany do degree convocations, they are mostly considered a vanity event that is only attended by narcissists, graduates of law, and people from cultures where such things are common – I know nobody who ever attended such a ceremony.}

Although correct, aeismail's answer seems bureaucratic. You've passed your degree, list it on your CV, and list your overall grade too. E.g.,

MM'XX -- Dec'17 BSc Subject (Grade), University, country

You can list your classes and grades in those classes too. E.g.,

Class A (X%), Class B (Y%), ...

Anyone reading your résumé wants to know what subject you studied, possibly what classes you took, and what grade(s) you got. Whether your degree has been conferred is less interesting. Moreover, if you're submitting your résumé in the same country as you studied, then the reader will know that your degree hasn't been conferred (because they understand the local system and they've seen lots of résumés).