The blog quotes a piece in Contract Journal, which cites a call by Lord Berkely to re-open the mail rail route, which closed in 2003, and use it to ferry waste from the Crossrail shafts and stations out of the capital. Berkely claims Crossrail's excavation sites will add 200 trucks per day onto the capital's streets, and he believes utilising the mothballed network, which conveniently runs beneath such key sites as Tottenham Court Road and Bond Street, could reduce that number.
It seems the plan was considered by Crossrail, before the project's board rejected it. While there are certain advantages in the scheme — and the network is kept in running order, so there would be little technical challenge — the rail only runs between Paddington and Whitechapel, so there would be a logistical problem in disposing of the waste at either end. Furthermore, the rail's narrow gauge could present difficulties.
So, perhaps not a revival for the mail rail just yet, then. Since its closure there has been some discussion about what to do with it — in 2003 a report offered suggestions including transporting wine to London's vintners — but thus far nothing has happened. Perhaps if it were put up for sale, like the telephone exchange in Holborn, it would have a chance of being revived in some way, but until that day it will remain one of the capital's many chthonic treasures.