These should be possible to all tags containing Text.

Example cfmail:
<cfmail to="" from="" subject="">
  My ultra cool mailcontent blah
</cfmail>

<cfset content = "My ultra cool mailcontent blah">
<cfmail to="" from="" subject="" text="#content#" />

So it would be possible to do things like that:
<cfset local.mailContent = getMailData()>
<cfmail attributeCollection="#local.mailContent#">


and also in Railo (im not quite sure if that is correct, i don't use that syntax often):
<cfscript>
    mail to="" from="" text="#local.content#";
</cfscript>