I am on net10/straight talk BYOD.
I may be wrong or incorrect or some what correct.. about this but what I am thinking is this is what happens on Net10/ST program.
Once An OEM release and Update and it is on Microsoft Server's and Available in North America then update becomes available for your phone.
I have branded AT&T Focus Flash and recevied Tango and Samsung Update the day that is was released in North America. Back at end of June, some are just now getting the update that are AT&T Customers themselves.
I can only speak for Samsung Phone's on ST..
Some Nokia Users for Sure now that network app has been released maybe they can chime in..