Thanks!  Worked like a charm once I set the context correctly:

   	<xsl:variable name="allReqs"                    select="/
descendant::PERSON[REQ]"/>
   	<xsl:variable name="allNames"                   select="/
descendant::PERSON[NAME]"/>
   	<xsl:variable name="allReqsWithNames"
select="$allReqs[count(.|$allNames)=count($allNames)]"/>
   	<xsl:variable name="allProjected"               select="/
descendant::PERSON[PROJECTED]" />
   	<xsl:variable name="locationNodes"              select="/
descendant::PERSON[LOCATION=$location]"/>
   	<xsl:variable name="allBackFill"                select="/
descendant::PERSON[BACKFILL]"/>
   	<xsl:variable name="allOpenReplacements"
select="$allReqs[count(.|$allBackFill)=count($allBackFill)]"/>
   	<xsl:variable name="locationBackFill"
select="$locationNodes[count(.|
$allOpenReplacements)=count($allOpenReplacements)]"/>

      <xsl:variable name="countLocationNodes"
select="count($locationNodes)"/>
      <xsl:variable name="countLocationReqsWithNames"
select="count($locationNodes[count(.|
$allReqsWithNames)=count($allReqsWithNames)])"/>
      <xsl:variable name="countLocationReqs"
select="count($locationNodes[count(.|$allReqs)=count($allReqs)])"/>
      <xsl:variable name="countLocationProjected"
select="count($locationNodes[count(.|
$allProjected)=count($allProjected)])"/>
      <xsl:variable name="countLocationReplacements"
select="count($locationBackFill)"/>