SIM unlock US Cellular variant?

[gwest1000]

I've been looking around for a while, trying to figure out the answer to these questions but can't.
-If I buy a moto x US cellular variant (contract free, off ebay), can I SIM unlock it and use it on a GSM carrier (like Bell in Canada)?
-Also, do the different variants have different radios?
-Also also, if I buy a new unopened moto x off ebay, is the warranty still valid?

Thanks for any info!