A quick q: I don't follow the citizenship certificate issue to know how long they take to get issued. What are the chances you would get this before you depart or receive after you depart and able to get someone to scan it to you? Because I assume you'd feel much more comfortable entering at a land border with a document (even a photocopy/scan) that says you are a citizen.
I also don't know what if anything they 'issue' you at the end of the oath ceremony to say done, apart from the cit. certificate.
I can understand why you would be cautious otherwise - and I wouldn't generally recommend this. (The only course that should be recommended is entering with valid docs and all that). And I don't have experience with it personally. But it's not at all rare for PRs to enter at a land border with no currently valid document - eg an expired PR card or photocopy of same, or COPR. In a few cases I've heard referred to here - with just the UCI, because that lets CBSA look the person up, although those were PRs.
I dont' recall having seen a case of a citizen exaclty like yours. But I have seen ones of eg US/Cdn dual citizens - children - where all they had was evidence they'd submitted for citizenship - i.e. they were presumed citizens at that point. (I don't really recall unfrotunately whether they were technically admitted as citizens or as USAians.)
And of course, there are lots of cases of citizens abroad who get robbed or lose all ID, etc. They're issued passports without coming up with originals - routinely. (Yes, their relatives would likeliy send copies of supporting docs - but if they have a passport, they're in the government's files).
But I believe the CBSA officers take seriously the statute that they SHALL admit those who (satisfy the officers that they) are citizens or PRs. The trick obviously is what is meant by 'satisfy' - but I think the documentation that you were a PR, had an oath ceremony, and that you-are-you and they can find you in the database is enough to satisfy.
That said - no guarantees, I'm not empowered to do that. )
And with any bureaucracy, impossible to know.