Entering Canada to catch a flight from YYZ
 

I live in upstate NY and normally when I fly to Germany or the UK, I simply book a flight from YYZ and drop my car at a lot or hotel. Now that vaccines are being used (got my shots TG!) and some travel restrictions easing, I would like to see my son in Germany. But what are the problems in crossing from USA into Canada if my objective is to park my car and fly out of YYZ?

the border is closed to all NON ESSENTIAL travel, of which making use of the convenience of flying from YYZ to Europe would fall into that category

Right now, you'd have take a quarantine after entering Canada before you could park and fly out of YYZ, just extended to March 31. They keep extending it over and over and over again, but only a month at a time, and only a week or two before the previous extension end date. So it's unknown at this point when USA people will be able to enter Canada without a long quarantine first.

You have have to keep with the conditions for USA people to enter Canada, not just to enter Germany, if that's what you're planning to do.

There is no hotel quarantine when entering via a land border. While there is still a 14 day home quarantine when entering by land, it is perfectly fine to leave Canada before that 14 days is up. I think you may be thinking of the scenario of entering as a non-Canadian by air for specific reasons (must stay the full 14 days), but that isn’t the case here and is just muddying the waters. One must just quarantine during the time they are in Canada. However unless nylicence is a Canadian citizen or PR, s/he will not be allowed to enter Canada by land (or air for that matter) so the entire thing is moot. The land border is closed to all non-essential travel except for returning citizens, PRs and certain other exceptions.

Before worrying about the intricacies of quarantine and the land border, what is your basis for entry to Canada at all? Similarly, what is your basis for entry to Germany?

Not worth worrying about anything else until you have those two matters clear.

No hotel or home quarantine if in transit in Canada. I do it all the time as a cdn citizen non resident. If the flight was not immediately after you entered Canada then you quarantine anywhere until you leave Canada. But you (or anyone) absolutely can exit Canada at any time with zero restriction.

There is a risk CBSA may not let you in via land if they don't believe your story you are going to catch a flight out of YYZ. What are you going to do if that happens?

Least risk is to make a connection within the US to your transatlantic flight.

A boarding pass and return ticket with an appropriate amount of luggage for the length of the trip should suffice IF you are a cdn citizen/landed immigrant. But with no status in Canada my bet is they deny you entry.

I don't understand why you don't just fly out of NY. I'm sure the prices are cheaper from there too to a place like Germany.