FranticFish - 10:12 am on Oct 27, 2010 (gmt 0)
I've seen this recently on a site I manage. The site home page is optimised for Phrase A and Phrase B. When I search for Phrase C (which is closely related) that page is returned in the results with Phrase C substituted for the actual title tag. The site has a number of IBLs that contain Phrase C and it has always ranked for Phrase C.
I'm sure it helps CTR.
I would imagine that the rationale is that, as legitimate anchor text in IBLS is considered 'part of the page', why not reinforce that for the searcher and confirm that (according to Google) the page is indeed relevant to the search phrase?