This ticket proposed using Group and/or an additionalReporter extension to support ad-hoc groups of providers as the reporter:

https://jira.hl7.org/browse/FHIR-38002

However, given that Groups cannot be perform actions, they can only be acted on, the resolution for the above ticket removes Group as an option for reporter, and suggests that the use case can be hit using an Organization, potentially an ad-hoc Organization as a way to model the set of participating providers.

Create an example in the DEQM IG to illustrate this use case and add discussion about this case in the general guidance on reporting.