Do remember the distinction between transformation and serialization. The transformation creates nodes in a result tree, the serializer turns the result tree into XML markup.
You can't put a CDATA section in the result tree, because there's no such thing in the XSLT/XPath data model.
You can however request the serializer to insert CDATA sections for the contents of any given element, by
<xsl:output method="xml" cdata-section-elements="NewUrl"/>
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference