The XSL stylesheet cannot perform the function of reading in the HTML file
as escaped programlisting text. You can use the document() function to
open another XML file (assuming it was XHTML), but it cannot parse it as
"text".
You might consider a preprocessing step that constructs what you want before
the xi:includes are consumed by the parser that understands XIncludes.
Bob Stayton
Sagehill Enterprises
bobs@sagehill.net