tangor - 9:04 pm on Jan 18, 2014 (gmt 0)
It has been my expereince (since 1996) that no search engine (and I mean ALL OF THEM) ever forget a url they have crawled.
Whether it is an accident that these old urls get back into the crawl, or deliberate, that I can't say, but they are definitely still in their index. I can say that pages GONE 410'd "way back when" are still, from time to time, (re)appearing in my logs.
I don't think there is any way to make them go away.
Conversely, on the side of the search engine (any of them), I wouldn't take a website's word that the page was REALLY gone... it might come back and then what?
These days I just ignore it, keep the site(s) clean and move on.