... a custom XML filetype that only extracts the text you want. The help gives some good examples of how to do this here: http://goo.gl/jBJ6jD
Hopefully you will only need one rule to extract the translatable content from the CDATA section but without seeing the file it's hard to know for sure, and it's also hard to know whether you have something a little trickier like HTML inside the CDATA sections.
Have a go and if you get stuck feel free to send the XML file to me and we'll take a look (but no guarantees we can do it!)
It may also be worth asking your client for a filetype... perhaps they have the expertise inhouse?
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