I've been unable to fine who my "hacktivated" iPhone 4 is locked to.
I've read there is a way to find out by model number but I can't find the number on the "list"

Mc605c

I am in Canada btw using a 3.10bb hacktivated iPhone 4

I've googled and haven't found anything either...

You sure it isnt mc635c? That would make it a Rogers iPhone.

It could be Telus, but to be honest, where multiple carriers offer the iPhone in one country (and also offer unlocking) - it's impossible to match carrier to model number.

Easiest way to tell is to set up an appointment at an Apple Store genius bar and ask them. They have a database where they can input your IMEI and see the carrier status. It's also possible if you get the right Genius on the phone you can get them to provide this information in a phone call, but reports around the internet make me think this is very hit or miss, where I have absolutely gone into an Apple Store before and asked them and had them look it up and give me the answer. I did it recently with an iPhone 4 that a friend of mine bought that was supposed to be 'carrier unlocked', but ended up being locked to O2.