The original GT46C ACe met USA Tier III standards.4600 class are apparently 'GT46CU-ACe Gen III (3)' hence the new look.These are described as GT46CU-ACE Gen 3 locomotive, so is Gen 3 in this case the same as USA domestic locos Tier 3 standards?
EDIT; would these particular locos that are now imported into QLD meet present day USA domestic emission standards for new build locos to run in the USA?
The 710 engine can't meet Tier IV without exhaust aftertreatment.
One locomotive has been built with a 710 engine and aftertreatment, a rebuild by Norfolk Southern.
As far as I know it has not entered service.