This solution does not use tiles expressions but will work if you need to display localized text in JSP when key is passed through tiles definitions.
In tiles definition:
<put-attribute name="title" value="htmlheadHeading1" />
In your JSP then use Struts2 <s:set>
tag to set title from tiles definition to local variable and then use it in <s:text>
tag.
<s:set var="title">
<tiles:getAsString name="title" ignore="true"/>
</s:set>
<s:text name="%{#title}"/>