I personally had no luck in seeing any of the replacements today, but it seems Peter Barclay managed to find one!
Either they were running >5-10 mins late or they were running >5-10 mins early, as I tried on three occasions to get 'em!

Croft Coach Travel's Sunsundegui bodied Volvo B12M, SA02CCY, was utilised on one rail replacement service today.
http://www.flickr.com/photos/27204054@N07/9484555041/