Hi @jgkinnear, that a good question. Currently we do not have an API method to verify this.
So probably you could try to do one of the following things to get your requirements:

1. Add an additional callback function to checkForUpdate method and rise this callback e.g. after this LOC. If you could create a PR that implements this and update docs - that would be much appreciated.
2. You could try to import some stuff from cordova-plugin-code-push, say you need to import
   class Sdk and class LocalPackage and try to write you custom function reflecting the same logic we do in checkForUpdate method. So this way you should be available to implement your custom handling there.

Please let us know if you have any questions regarding this.

Hi @jgkinnear, please also take a look at the similar PR here microsoft/react-native-code-push#888 - it could help you. And especially pay attantion on microsoft/react-native-code-push#888 (comment)

@jgkinnear - we believe that we can close the issue if you do not have any questions at that moment. Do not hesitate to reopen the ticket if needed.

Thanks for the information @sergey-akhalkov and @max-mironov, appreciated!