An event is commonly published to a single topic and doesn’t need to be published to two. When a need is to fan out that event, you could set up a subscription on the topic used by NServiceBus and configure the auto-forwarding to any arbitrary destination you’d like (topic or a queue). You can control wherever a specific message or all messages will be auto-forwarded to the other team’s topic on that custom subscription.
Should you require more details, I’d advise opening a support case at https://particular.net/support, referring to this thread.
The other team could also run their Function with NServiceBus and would not need to go through this hassle. Let them know about NServiceBus support for Functions (https://docs.particular.net/previews/azure-functions-service-bus).
Have a great day.