Can you use sprint and nextel phones for boostmobile plans and not just the boostmobile phones?

some older model nextel phones will work the newer ones dont and sprint phones dont use a sim card so you cant use them if you have the boost with no sim no u cant use sprint|||any of the older(i90c, i530) and newer(i880, i775) NEXTEL phones will work except the blackberries, i920 or i930 and the ic model phones as they are sprint and nextel on one phone. as far as sprint units u cannot use them on boost at all.