Short connection in YYZ, CAN to USA?
 

Hello,

I will be travelling from YVR to BOS, and since I have a bus bound for Providence to catch, the only option is a 1 hr 19 min layover in YYZ.

I will be flying UA, with a checked bag. The vast majority of places I've looked has told me that I will need to pick up my bags, so I suppose that's the case, because Pearson's website is confusing.

Do I have enough time to go through US Customs and move my bags?

When is that transit. You chance of making it varies whether it is Monday morning or Thursday/Friday afternoon.
Is UA the operating carrier or are they code sharing with AC?

You might not have to pick up your bag but they need to id the bag at US CBP to clear it into the US.

1 hr 19 minutes is a tight connection. Very tight Monday morning or Thursday/Friday afternoon.

You will not have to pick up your bag at YYZ on a domestic - transborder connection in Terminal 1. However, you will have to wait in a special transit hold area until your name appears on a screen (i.e. your bag has been matched in the bowels of YYZ) before you can proceed to customs and through security again.

1h20min is not impossible but tight, especially if you don't have Nexus / Global Entry for the US.