Hi, It depends on the licenses your client have purchased. You could have a look at the following link that contains the Oracle global price list information. To my understanding additional license is required. However, I would suggest you to get in touch with Oracle POC to know the exact status.
https://www.oracle.com/assets/technology-price-list-070617.pdf
SOA Gateway is not bundled with SOA Suite.
Oracle SOA Suite has oracle JCA E-Business Suite adapter to communicate with EBS.
Regards!