If you are simply looking to download NBR files, I suggest using NBRFileOpenService.downloadFile, which does not use the ticket value and instead takes site admin username, password, siteId, and recordID. It also has a required element, serviceName, but that can be null. downloadFile provides the same response as downloadNBRStorageFile. Last I checked, which was some time ago admittedly, authentication tickets worked the same for either service and could be used cross service. NBR API generally requires site admin credentials, I would need to test further to confirm if host access could be granted to a subset of APIs. If you are trying to use getMeetingXml, then I would just go with getMeetingTicket from the same service.