Yes, Work and Study are essential purposes as per the government.
But,I read on this forum(under foreign workers section) about someone getting denied entry with open work permit in April and back then the website wasn't updated about having a work contract for workers. And in her case, Airlines checked in with CBSA who presumably denied her boarding.
Again, i don't know what actually happened because i wasn't on the ground situation.
I heard colleges in Ontario were sending students who had a compulsory in person session in their portion of studies 'Arrival Support Letter'.
denied boarding by airlines is still better than denied entry by CBSA