The international version should work. Not sure about the T-Mo version, I don't know what bands it uses.
Sorry, What I meant is will it get by the system sweeps. As in, can you use it on the dumbphone plans without getting the dread "we added the appropriate data plan......." text message. Both versions will definitely work on with ATT's HSPA (3G) and the RM-893 (T-Mobile version) should work get LTE on ATT's network (with the appropriate data plan) although I don't think anyone has confirmed this as of yet.