Hi Whistler
It is not something that I am aware of, do you have POA? You usually need a Dr's or Psychiatrist letter stating that the person cannot attend an assessment centre and require a home visit.
Your post raises a few questions such as, is your wife in receipt of ESA now and has been asked to attend a re-assessment, as you cannot claim IR ESA now, you have to claim 'new style ESA' which is UC based.
Does your wife receive PIP/DLA?
Check out the National Autistic web site:
www.autism.org.uk it has excellant information.
I have had a quick check and cannot see anything about not having to undergo a face to face WCA assessment.
Gary