"Do these Branch buildings immediately go on the For Sale Market or have the GB been looking for buyers on the down low prior to announcing the closures."
Unlike the sell offs in New York where the buildings can usually be sold for a good profit on an active brownstone market as condos , regional branch offices have a somewhat restricted number of purchasers. From what I heard of the Irish Bethel , the JWs there had absolutely no idea of the closure & there was no evidence of any due diligence or offering of the property to prospective buyers. It is still on the market without any obvious purchasers. http://www.mol.ie/property.aspx?id=192 at about 1/3 of the price the society could have got at the peak of the Irish property boom in 2007.
The New Zealand Bethel was touted around a few buyers before being sold to the Eilm Pentecostal Church http://www.stuff.co.nz/auckland/local-news/manukau-courier/9124458/Witnesses-sell-Elim-buys
I honestly don't think the primary purpose of these sell-offs is to cash in on the buildings. Many of them literally are no more than a small accommodation block and a few offices. I think the main purpose is to centralise in the USA & remove the societies "footprint" from as many countries as possible.