Google search on Quest Lab Canada landed me on Exam One labs as a company with Canadian offices so obviously they accept some Canadian insurance
Here is the Canada website
https://www.examone.ca/all-locations
and they also have some US locations, the nearest in Inverness
Examone Location Search
Now this does NOT mean that the US locations also accept Canadian coverage, but it might be. Also note that this company is associated with Quest itself as its full name seems to be
Lab One a Quest Diagnostics Company.
The most important question to ask is not whether they accept your insurance but rather how do they process the claim. They must accept your insurance as payment under the same methodology as it would be processed in Canada. For instance if your coverage pays 18.00 Canadian for the Chemistry Screen and you would pay $1.80 is that exactly how it is handled here. You don't want to hear later, yes we accepted the 18 dollars but now you owe the full difference with no write off. "We accepted your insurance"