<xsl:template name="abc">
        <xsl:param name="prefix"/>
        <xsl:param name="track"/>
		
		<xsl:element name="{$prefix}A">

</xsl:template>


<xsl:call-template name="abc">
                    <xsl:with-param name="prefix">reg</xsl:with-param>
                    <xsl:with-param name="track">anyway</xsl:with-param>
                </xsl:call-template>

<xsl:template name="address">
        <xsl:param name="prefix"/>
        <xsl:param name="test"/>
<xsl:element name="{$prefix}Region" namespace="http://opopop.ru"><xsl:value-of select="//pgu:object[pgu:code = $test]//pgu:entry[pgu:key = 'Name']/pgu:value"/></xsl:element>
</xsl:template>

<xsl:call-template name="address">
                    <xsl:with-param name="prefix">reg</xsl:with-param>
                    <xsl:with-param name="test">abc</xsl:with-param>
                </xsl:call-template>

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:app="http://opopop.ru">
</xsl:stylesheet>

<regRegion xmlns="http://opopop.ru">такой</regRegion>

<xsl:stylesheet ... xmlns:app="http://my.company.com">
.............
  <app:test>
  .............
  </app:test>
...........
</xsl:stylesheet>

<regRegion xmlns="http://opopop.ru">такой</regRegion>