In reply to a post by Fastman2:

a cab can easily be in place for 6 months prior to being live
there are also extended issues where you have something called live to live and that have to be resolved prior to the cab being open for orders

or alternatively the cabinet is opened for orders before the live to live is done but Openreach's migration team doesn't tell any one even in Openreach that they have not done the work, leading to several people having their service cut off for weeks, many abortive Openreach engineer visits, and general confusion all round before the resulting mess is sorted out.

And chocolate hobnobs which I hear are what Openreach engineers prefer