I am not ware of any search engine being effected by mark-up per se'. That is, they may display mark-up, but it will not necessarily effect performance. The reason is simple. It is easy to game the system.
Google and Bing can see if a page has changed and will use the only date they have in the header, the resource modification date. However, some CMS/blog software can/will stand in the way of this by presenting the current date and time as the resource modification date. Which ones? I have no idea. If this is the case, then I suspect that Google and Bing will use the fetch date and time which would end up being the same anyway.
I do not expect that using the meta tag as you have suggested would hurt. You can certainly try it and see if there is an advantage. Even if there is no obvious advantage, there may be advantages elsewhere with sites other than search engines. Who knows. This may be a perfect opportunity to research and become an expert on this very subject and possibly on other similar topics.