Yes, UPS has expanded Central and South American operations.
UPS was partnering with Challenge Air Cargo for a few years then last year UPS bought Challenge. Where you would see some UPS aircraft fly on behalf of Challenge and Challenge aircraft flying for UPS you will now see all UPS aircraft except for adhoc charters. UPS did this to aquire the vast operating rights Challenge had in these areas.
In quite a few North American destinations the 75 flew into, they have pulled those aircraft out and replaced them with 72's and DC-8's so the 75's can fly the Central and South American routes.