Just checking if anyone can provide some insight if Eastlink locked iPhones will work with any other carriers without being unlocked?

I know that a Telus iPhone will work with Koodo and a Bell iPhone will work on Virgin without unlocking and vice versa.

This is what I'm seeing with an Eastlink iPhone 5s:

Bought it used and it was activated and had Eastlink carrier settings listed. I inserted a Telus sim and the phone went into the activation lock due to the unsupported sim (you have to remove the unsupported sim to get it working again). Then inserted a virgin sim and the iPhone activated and shows Bell carrier settings.

So it looks to me like an Eastlink iPhone will work with a Bell/Virgin sim without unlocking?

Just to provide more info the phone is clear and is not on the imei blacklist it is also not icloud locked. I am able to use my Apple id on the unit.