The 2011 Census output area boundaries were released by ONS on 30 October 2012. The ONS release constituted a single dataset covering the entirety of England and Wales.
The GLA has extracted the boundaries for each London borough and provides them here in MapInfo (.tab) and ESRI ArcGIS (.shp) file formats.
Included are Output Area (OA), Lower Super Output Area (LSOA) and Middle-Level Super Output Area (MSOA) bounadries.
Each geography is provided at Extent of the Realm (BFE), Coastline (BFC) and Generalised Coastline (BGC).
More details about 2011 Census geography can be found on the ONS website: http://www.ons.gov.uk/ons/guide-method/geography/products/census/index.html