You can include a file using a layout from another using a layout without having the layout appear twice on the page. To do so, you must use the "include" functionality of Layout Components, which does have some restrictions.
Other than those restrictions, however, everything should work as you would expect.
<cf_Template title="Page Title">
<cf_layout include="/mypage.cfm">
</cf_Template>
<cf_layout title="Page Title">
<cf_layout>
<cf_layout include="/mypage.cfm">
<cf_layout>
<cfoutput>#layout.head("Page Title")#</cfoutput>
<cfoutput>#layout.body()#</cfoutput>
<cfset layout.include("/mypage.cfm",variables)>
<cfoutput>#layout.end()#</cfoutput>