I believe that they are certainly different part numbers and they appear to be a different shape so I assume that they won't fit. Enduro Engineering do a rear disc guard for the gassers but it only fits 2010-2014 models so I guess a 2011 won't be interchangeable with the older bikes.
It looks like the rear caliper support as they call it is the same for bikes 2001-2008. KTM parts seems to have them for $25 but that seems very cheap compared to elsewhere where they are going for $140.
http://www.ktm-parts.com/BE250022120.html