My sympathies to anyone who has had, or will have, travel plans disrupted by this failure.
Whether this is a software problem within the baggage transfer and delivery system or a facilities failure itself; it shows a lack of managment skills on behalf of the BAA in that they do not seem to have any back-up plan to mitigate the failure.
Any airport knows (or SHOULD know) the volumes of baggage going through their systems at any time; models worked on histories and flight programmes can acurately predict the anticipated volumes.
BAA should be held to account. Unfortunately I would predict that the airlines will not be able to take action because of the terms and conditions imposed by the BAA for operators and there is no breech of contract involving individual passengers as they have no direct contract with the BAA.
Will T5 be any better - don't make me laugh, almost guaranteed that there will be major disruption at some stage within the first 6 months of opening.
The BAA are more interested in investing in ambience to encourage shopping than rock solid infrastructure behind the scenes.