Resolution: The feature of exposing WSDL as an HTTP service to Trading partners through BC is currently not supported.
BC-SOAP Protocol allows you to create a WSDL based on the service/Operation created.
You will then have to provide the WSDL to your Trading Partner, who in turn will import it in their B2B gateway.
Alternatively one could host a separate web server (totally independent of BC) to expose the WSDLs and provide this web server's URL to your Trading Partners for fetching the WSDL.