Generally agreed. CDMA providers exercise deep control over the phones they permit to be used. It's partially pragmatic (the PRL, or preferred roaming list, must be correct to make sure the phone uses the appropriate towers with the appropriate priority) and partially dogmatic (they seem to like to exercise control over the hardware you use).
GSM carriers like Rogers can't and don't exercise that level of control. Their own phones are generally locked, but you can buy an unlocked phone and use it. They don't guarantee it will work perfectly, but will still provide some help if you can't get it working fully. I have used several different unlocked phones with Rogers with good success. Using an unlocked phone is useful in other ways - for example, you can buy a prepaid SIM card when you travel to other countries, and pay much less to make and receive calls or use data than you would pay roaming with Rogers.
Unfortunately, the Rogers network is very limited in the original poster's province of Newfoundland.