That is hit or miss with Safelink. They have their SIMs locked to the phone it was issued to. I took my Gma's Safeline SIM and put it in another Safelink branded phone and it would NOT work. It said invalid ESN even though the replacement phone worked with its original sim. That was on the T network though.
And you do realize that TracFone, Net10, Straight Talk and Safelink are the same company right?