Not Part 133
Those mentioned are not Part 133.
They are civilian operators operating in Public Use status. They are contracted to US Department of Interior/National Park Service. The contract allows them to operate in Public Use status because the mission cannot be performed Part 135/Part 133.
Most helicopter rescue missions in the US are performed by government agencies in Public Use status.
The aircraft performance requirements posted by JimL for Part 133 are very difficult to meet in any aircraft in a real mission configuration (depending on weather the day of the test). Several have a testing configuration and real mission configuration.