This presentation by Axway at the OASIS Open Standards forum references a large scale deployment of ebXML Messaging in Asia.  The exchange of customs documents between Thailand and the Philippines uses ebXML Messages. 

Via service providers, this link connects many  thousands of exporting and importing companies.  

http://events.oasis-open.org/home/sites/events.oasis-open.org.home/files/Rizk.pdf 

Jagdip Grewal, Chief Technical Architect, NHS Connecting for Health, presented at the OASIS Open Standards forum in London.  Connecting for Health is a large scale deployment of ebXML Messaging.  Electronic Transmission of Prescriptions are a five hundred messages per second. This may go up to seven hundred, the audience was told.

http://events.oasis-open.org/home/sites/events.oasis-open.org.home/files/Jagdip.v2.ppt