Hi, Wolf, and thanks for your question!
InterSystems IRIS is not generally compatible with Caché or Ensemble, including the security settings. The best way of going from Caché or Ensemble to InterSystems IRIS is the in-place conversion, which preserves the data from the Caché or Ensemble instance. With the in-place conversion, export and import are not required. (Compatibility features are documented in the InterSystems IRIS Adoption Guide, which is available from the WRC.)
Yes, @Evgeny Shvarov -- see the sections "Exporting settings programmatically (from classes in the Security package)" and "Importing settings programmatically." (They were a little hard to find because of the size of the headings, but now they're more visible.) The relevant classes are in the Security package, and there's class reference documentation for them at https://docs.intersystems.com/irislatest/csp/documatic/%25CSP.Documatic.cls for the most recent version of InterSystems IRIS.
For InterSystems IRIS content on emergency access, see https://docs.intersystems.com/irislatest/csp/docbook/Doc.View.cls?KEY=AS....