Hi
I am not sure if I understand you requirement correctly :
1. Yes SAP can consume third party Web services ( When you import third party WSDL into SAP we just need consider certain limitation).
http://scn.sap.com/thread/750378
2. In your case you need to configure SAP Consumer proxy(Consuming third party service) . (Logical Port or PI)
Thank you
Regards
Goverdhan Totawar