In some cases it is possible to have a multi-service CSPC, though this would typically indicate that there is a dedicated engineer available for technical assistance required to map one CSPC between both services.
Otherwise, it is understood that a single CSPC certificate is good for a single Inventory+portal combination. If a CSPC is already deployed, but not sending data to SNTC then a new CSPC+Certificate would be beneficial so that administrators can control where their network data is sent to (one certificate = 1 service/portal/inventory).