Harsh,
I spent a lot of time dealing with the Catalog services writing an application to integrate with the MII virtual file system via FTP. I could be wrong but in my experience the Catalog service will not return the file in a way that the ui5 localization infrastructure wants. It returns a file containing the properties file as an encoded string. If there is a way to use the Catalog service to get the localization files then Pradip or someone else will have to provide a more complete example.
Regards,
Christian