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I have not heard about WSDL or SOAP web services on TREP or EAAS. TREP APIs provide only functionality to consume Real-Time data and it's not a web service or SOAP/WSDL. I'm not sure what's the name of the WSDL service your client use previously. It sounds like the service was their own web service product which consumes the data from EAAS and provides data back to their client app.
I would suggest you confirm with the client about how they use it first and then checked with the EAAS support team directly if they have any product which supports SOAP/WSDL.