Yes.  WiMAX is a Global Standard that has certified products shipping worldwide and interoperate with gear in the same frequency range and power range.  It is important to note that different countries utilize different spectrum frequencies for broadband delivery.  For instance, the licensed band 2.5 GHz range in the US is also widely used around the world.  However, the widely used international broadband spectrum range in the 3.5 GHz channels is not available in the US, although the FCC has recently opened a small slice of lightly regulated spectrum in the US at 3.65 GHz that uses the same WiMAX radios.  The early waves of WiMAX products are not intended to function in multiple WiMAX spectrum ranges simultaneously.  However, some of the early WiMAX radio sets may incorporate WiMAX/GSM or Wi-Fi dual connectivity from the beginning as several vendors appear to be engineering this capability into some Mobile WiMAX radios.  A dual WiMAX/GSM handset is already on the market in Russia.