International Pax upgrades into business class? SCL - EZE - SYD

It was my understanding that unlike domestic flight, there are no upgrades for passengers from the coach cabin into the business elite cabin. But watching flights from EZE, SCL, SYD and other back to the states I am seeing many UP1, UP2A, UP2B, PSUP etc priority codes on the standby list, often displacing most or all of the nonrev's out of the business cabin. Can anyone shed any light on this?

Thanks.

They are medalion member upgrades. They are using their points to upgrade to first/business class. PSUP is an employee on company business travel asking for a upgrade.